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Claude Opus 4.5 vs. Gemini 3 Pro: The Ultimate AI Coding Showdown for SaaS MVPs

Claude Opus 4.5 is here, and people are saying it is the world's best coding agent. I needed some proof, so I put Opus 4.5 head-to-head with Gemini 3 Pro. I built a SaaS app and I wanted to see who would win, and the results might shock you. I did it with my friend, The Boring Marketer. In this article, we are going to show you how Opus 4.5 stacks against Gemini 3 Pro, and also how you can get the most out of Opus 4.5 (hint: it has to do with setting up Claude skills, and we show you exactly how to do it).

Market Context: The Rise of Agentic Development

I am an expert analyst and I believe the era of the "idea guy" is upon us. The barriers to entry for building complex software are dissolving rapidly due to advanced LLMs. By 2025, the market for AI-powered code generation tools is projected to exceed $1.5 billion, driven primarily by the adoption of advanced multimodal models like Opus 4.5 and Gemini 3 Pro in rapid prototyping and MVP development.

Claude Opus 4.5 vs. Gemini 3 Pro: The Ultimate AI Coding Showdown

I built a SaaS app and I wanted to see who would win, and the results might shock you.

We got The Boring Marketer on the pod, James. By the end of this article, what are people going to learn? Well, I'm just going to open the curtains and show everyone sort of how I'm using the latest models. I want to dig into Claude Opus 4.5, I want to jam a little bit on Gemini 3 Pro, and I want to show people how I'm building landing pages and websites as a non-designer, non-engineer that are driving great conversion. Can we live play with 4.5 Opus 4.5 and see what happens? Let's do it. Let's do it.

And I also think something that would be kind of interesting is if we did sort of like a test. So, let's use Opus 4.5 with a front-end design skill, let's see what we can come up with, and then let's do Gemini 3 Pro with the same prompt and let's see what we can come up with there as well. Let's do it.

The Test Concept: Building an Estate Dashboard SaaS MVP

Estate Clear creates a real-time family dashboard where executives can post updates, upload documents, and track progress while family members get instant notifications instead of playing phone tag.

Here's a way we could do this: you want to get an idea from IdeaBrowser.com and run that and see what it comes up with? Sure. So, do you want me to give you today's idea of the day? I actually really like this idea: Estate Dashboard for keeping families informed during probate. Estate executives face constant phone calls and texts from anxious relatives saying, "What's happening with dad's estate?"

I mean, it's one of those small ideas. Like, there's not how many estates are there? Not millions in the US, at least I don't think. Actually, maybe there are, I don't know how many, but I've gone through that process before and, you know, it's a black box and it takes over a year. You have no idea what's going on. You're getting these replies from lawyers and stuff like that. Give me the DoorDash visual that's like just letting me see what's going on, you know? Yeah, and you'd probably save a lot of money on billable hours to attorneys going back and forth asking them questions and stuff. And the retention is probably insane; you're not going to cancel that. All right, let's get to it.

Prompt Used for Both Models: I want to create a conversion-optimized landing page for my new startup. Build an HTML that I can view locally. (Note: Opus 4.5 prompt included the instruction: "You must use the front-end design skill.")

Round 1: Claude Opus 4.5 Landing Page Output

I like the overall aesthetic of this; it has a nice, subtle tone to it and is not screaming in my face with a bunch of wild colors.

So, here we go. This is Opus 4.5 with the front-end design skill one shot. We have the description from IdeaBrowser.com and literally like a one- to two-sentence prompt. "Stop answering the same questions from everyone in the family." So good. Estate executives face constant calls and texts from anxious relatives. Estate Clear gives you a private family dashboard where everyone stays informed without overwhelming you.

Clearly, it is not just using the same kind of purples and typical AI stuff. So, let's scroll down and see what else it did. This is so I only told it to reference the design skill, actually. I didn't explicitly ask it to reference any of the copy skills, so I don't think that it's actually using those. I think this is just what Opus came up with. I think this is really awesome. This is definitely all you need for an MVP or getting something like this live.

Anecdotally, it does feel like we've with Opus 4.5 and Gemini 3, it does feel like we've entered a new stratosphere of vibe coding. I would definitely agree. I think that the lines are just blurring across the board. The line between a non-technical person being able to code blurred, and I would always feel very frustrated with the design portion of this whole process. You know, yeah, you can build stuff, but everyone can tell it looks vibe coded or it just doesn't look right. Now that line is getting blurred. So all these lines are just blurring, and it's not necessarily like vibe coding or vibe marketing or vibe designing or whatever; it's just like vibe building in a way, and the entire stack is just kind of coming together into one place, which is nuts.

Round 1: Gemini 3 Pro Landing Page Output

Keep the family united goes hard—manage the estate, keep the family united, stop playing phone tag.

Here's Gemini's version. The private dashboard for executives to share updates, documents, and milestones with the whole family at once. Very clear, clear, but I don't know, it doesn't have a—I like some of the animations on 4.5. I also like the layout of the 4.5 one. I can get the copy and I can get that initial visual right away without needing to scroll or scan down the page.

Social proof. This is very similar between both models. This section here: "It is the AI. Don't know what to say? Let AI write the update." You called that for sure. But I think that's really interesting. To me, I probably wouldn't have thought of this, and it's also, you know, if you're trying to create a startup right now that gets traction, I think having some of these AI-first ideas really help. I was curious. This is cool. It already built a little kind of like preview of some functionality here into the landing page, so I like that idea a lot. I like the imagery here. It feels more human, I guess, which is also something that, you know, coding models have missed in the past. Everything feels very robotic. You've got the emojis, you've got the same style of illustrations and stuff like that.

Man, it's tough. I think both are good. I think from a pure aesthetic standpoint, I think I like the Claude version better. That's just me. No, I think you're right there. I think objectively it was nicer. I think, you know, from the feature perspective, like I said, the AI feature is really interesting. Impressed that it worked, too. I mean, my real question with 4.5 is like, okay, great, now it's made a landing page, but can it create a SaaS app? You know what I mean? Like, ultimately, I'm interested in pushing 4.5 to the limits, and I would be curious if it actually could build an app that I can sell.

The New Era of Vibe Coding: Design and Logic Blurring

It does feel like we've entered a new stratosphere of vibe coding.

It absolutely could. I mean, you know, if you wanted to build this entire product in Claude code with 4.5, you could definitely do that. Like, with Claude 4.5 Sonnet, I've taken an idea for a SaaS from zero to production ready, so you can certainly do it with either of these models. Now, what I have personally found (and to be clear, I haven't tried to build a full-on application with Gemini 3 yet) but I think that Claude's earlier models, I would always go back to them. I was trying to use Codex and GPT-5 before 5.1 came out and Gemini 2.5 Pro and stuff like that, and while the logic is good and the thinking and the debugging is good, getting from zero to fully ready was easier with the Claude models. That's just been my experience. So I always kind of try to lean on Claude as the workhorse and then have these other models doing what they're good at as sort of an advisory model, if you will.

Round 2: Building Clickable Prototypes (Full MVP)

My take is I feel that Opus went a little bit deeper in terms of thinking through the product.

Here they are side by side now. I mean, if we wanted to, we could see how each of these builds out beyond the landing page and just say, "Hey, create a clickable prototype for the concept," and we can kind of get a gauge on how it's thinking there. Let's do that. Okay, and because I'm curious, let's do it. All right, let's go back to Cursor and we will get started there. So, I want to build the full clickable prototype of the app locally so that I can open up an HTML and see how it looks and feels.

And if we wanted to build the back end, we could. Oh, absolutely. I mean, we could set up the entire backend. Some of the things that I've used in my most recent builds are like Neon, which is kind of the database, plugs in nicely and plays well with Vercel. Clerk for OAuth and login, easy to spin up OAuth or anything like that. I would probably deploy onto Vercel or Railway or something along those lines. You could integrate Stripe for the payments and the subscriptions relatively easily as well, and you could build the entire logic and application here for sure.

I'll give the same prompt while we're waiting there to Gemini. One of the things that I really like about Gemini and just Google generally is how, and we've talked about this a lot, is just how vertically integrated it is. Now developers and stuff have their preferences for what tools and what things they want to use at different levels of their stack, but if you think about like 90% of people, someone who's just trying to build their app or get something out there or whatever, having everything integrated into AI Studio from OAuth to your storage or database to easily integrating AI models into your product to hosting, etc. Google has the full range of capabilities there that they own that they can integrate directly into AI Studio, which I think from just a convenience perspective for most people is a really powerful value proposition and from a cost perspective, from a speed perspective, from just keeping things organized perspective, that's a huge advantage that they have as they push this forward. Totally. I mean, I don't think I'm going to switch from my iPhone, but I've never been closer to switch to an Android.

Comparison: Claude Opus 4.5 vs. Gemini 3 Pro (MVP Build)

Feature	Claude Opus 4.5 (Winner)	Gemini 3 Pro
Aesthetic/Design	More refined, subtle, and professional tone (using Front-End Design Skill).	Clean, but slightly more generic "AI dashboard" look.
Product Depth (MVP)	Went deeper into core functionality (progress tracking, document storage, subviews).	Focused on AI-first features (AI update writer) and social sharing.
Vibe Coding Quality	High-fidelity, production-ready feel.	Solid MVP, but required more scrolling/scanning for core info.
Code Stability	Historically strong workhorse for complex, multi-step builds.	Encountered initial errors during the prototype build.

Debugging and Agentic Workflows

I'm thinking that its ability to work through the bugs without sort of getting lost is going to be a lot stronger.

So, something that I've noticed is there's a couple errors here. So what do you do when you see errors like that? Fix error. How can you make this work? No. You know, for me, it's yeah, just kind of a process of like trying to dig deeper into what the root cause is. So I use the terminal for all of the work that I'm doing. So if we think back to that Cursor setup, I may say, "Hey, Claude, ultra think about this problem." You know, if you type in ultrathink, it'll change colors and it'll use more power to kind of help to dig in or solve the problem.

Other tactics that I've used with Claude because that's like my daily workhorse is I'll say, "Hey, if I'm really stuck, I'll say, 'Hey, spin up specialized sub-agents that are going to go and find the root cause of why this thing is breaking. I need like a Q&A tester, I need a senior sort of like engineer focus on this or whatever.'" And then it'll spin up these specialized agents that'll identify different areas that they're going to go and research in the codebase, and then it'll come together with like a comprehensive sort of analysis for me. And then I can say, "Hey, all right, cool, plan this in terms of like a step-by-step process that we can go through to fix it." If it's still stuck, that's where I'll use Cursor agent with GPT or Gemini or something like that for kind of an outside perspective.

Now, one of the things that Anthropic is kind of talking about with Opus 4.5 is that its ability to kind of stay on track is really powerful. Sometimes when the code base grows, it's harder to kind of manage the context to find what that single problem or whatever is causing that's breaking the app. So I haven't built something full with Opus 4.5 yet. I'm thinking that its ability to work through the bugs without sort of getting lost is going to be a lot stronger, and I wouldn't maybe need Ultra Think or Sub-agents or maybe even those additional agents on the side. So I'm really curious to dig into that and see, which is a big deal. It's a big deal for your the health of your heart, yeah, for sure.

Testing Gemini 3 Pro in Anti-Gravity (The Agentic IDE)

I'm curious if we put the same prompt into the Gemini 3 Pro model in Anti-Gravity if it is different than what you get in AI Studio.

I have a feeling I know the answer to that, but I'm—let's try it. All right, we'll see what happens. My hunch is that you're going to get worse design out of Anti-Gravity. Okay, but you know, I've been wrong once and I've been wrong before. I've been wrong lots of times. So, okay, let's check it out. And by the way, Anti-Gravity is really cool. Definitely recommend people check it out. So I'm just going to paste in the same prompt and let's see what happens.

Why should people use Anti-Gravity over Cursor? Well, it's a good question. I mean, at the end of the day, they're both VS Code forks, you know, so they're both kind of based off of VS Code, which is open source and free. However, I like some of the things Anti-Gravity is working on. To be honest, I've just started using it and testing it and things like that, but they've got some like Chrome stuff built in here where it can access the browser in a really easy way, and it can even access—you install a Chrome extension. So if anyone's done vibe coding in the past and you're trying to squash a bug, you know, you open up your deployment, whether that's locally or hosted or whatever, and you know your coding model's like, "Hey, like navigate to it on Chrome and then open up like the console and the dev tools and figure out like tell me if this API connection is working, copy paste the responses." Like that whole debugging process is pretty painful. So with the Chrome extension that Anti-Gravity connects to, it can access that data for you programmatically. So it's accessing the DOM, it's seeing sort of the data behind the scenes.

I suspect it will greatly minimize the back and forth in this debugging process when it has a very tight browser integration and can access data through the Anti-Gravity extension. I think that's super interesting. That's kind of what the first thing that I've really kind of picked up on and noticed. I suspect, given the speed that Google's shipping, we're going to see a lot of interesting things here. Like some of the landing pages I've built here, I'm pretty sure you'll be able to have Nano Banana Pro integrated within Anti-Gravity and some of these other tools. Like, you know, like you want a killer illustration? Great, let's spin that up with Nano Banana and put it on the page. That's where it's going to go crazy, right? Because you see what's happening with Google is they're creating V3, they're creating Nano Banana, they're creating all these like, it's a whole creative suite of killer use cases that are pretty independent, but once they're able to bring that into Anti-Gravity and just use all the horsepower from all those killer use case products, I think it's going to be absolutely madness. It's going to be really awesome.

Anti-Gravity’s Nano Banana Integration

It is generating a custom dashboard mockup image first to make the page look real, then I'll build the HTML file.

So what's happening? Okay, so we put in the same prompt here as well. Right now, actually, I think it is generating a mockup with Nano Banana. So it's actually generating an image with Nano Banana instead of going ahead and building the page from scratch. Oh, wow. So it used Nano Banana. So it's integrated to create a high-fidelity visual mockup that we can see. Pretty nice initial mockup, I would say. Totally really nice. Like those chunky buttons. Also, that's kind of like how a real team would work, right? Like, okay, let's create like a high-fidelity mockup. Let's make sure you like it before we go and write all the code, you know? Totally. Anti-Gravity may surprise us here.

So, this is Anti-Gravity Gemini 3 Pro. Keep families informed during probate. Stop the endless phone calls. Estate Clear gives you a real-time dashboard. Share updates, documents, and progress with family members instantly. It's got the image that it created. So again, this is really cool how it's able to utilize Nano Banana within the workflow, call it as a tool, and implement it into your design. Like that is really neat. Some similarities here between some of the other ones in terms of showing the features and stuff like that, the pricing, etc. So I think, you know, my take would be outside of this image, it feels a little basic. So I think your instinct that AI Studio will have a better initial design output from one prompt was correct. I think what was cool about Anti-Gravity and this whole sprint that we did with it is if you scroll down the mockup, how that mockup is and how this is wireframed out, there is some alpha in there. And then, you know, maybe you go back to Opus 4.5 or maybe you go back to Gemini 3 Pro on AI Studio and then iterate there.

Mastering Claude Opus 4.5: Leveraging Custom Skills

A skill is just like a set of instructions that the model is going to reference when it does a certain task.

Going back to kind of like my setup a little bit, there are a few skills that I recommend everyone create with Claude Opus. So, I do a lot of website optimization for thevibemarketer.com. I want to figure out, hey, how can I convert more visitors into customers? And we've talked a lot about this, but it comes down to really good copywriting. I think that that's a struggle for like 90% of business owners is knowing what kind of copy to write for their business. They don't want to feel—you don't want to feel too cheesy, too salesy, but you also want to leverage the principles of influence and persuasion in the right way. You know, you don't want to have this empty brand speak, and you also don't want to be like, "Hey, make this much money, do this," like right away. There's a fine balance, right?

Skill 1: Elevated Direct Response Copywriting

I call this elevated direct response and I build a skill around it, and every time I write copy for my website, Claude references this skill.

It does a great job at producing this style of conversion-focused copy. So the way that I did it is I found some people in my space or in our space that I like, that I look up to, that have built some pretty huge businesses with community and education and things like that. So here's an example: I have the Perplexity MCP set up in Claude Code. I say, "Hey, use the Perplexity MCP, go research Cody Sanchez and Alex Hormozi and like the biggest sort of like education or information-based businesses out there and break down exactly how they're writing their copy, how they're positioning their products and services, and how they're talking about what they do. What are the main takeaways that you can learn?"

So I did that and kind of came up with a few different baseline insights: the contrarian educator. So Cody Sanchez starts out with like a contrarian point of view or a contrarian hook. When I did this research on Alex Hormozi, I found that he's got sort of these offers that you can't refuse, and he's always sort of stacking the value in terms of like what someone is going to get with this big promise that you're making. So those are great learnings. What I did was I collected that into kind of this elevated direct response skill or playbook, and then what I did is I fed Claude Code a bunch of examples of my own writing. So things that I've created, a bunch of tweets, even like transcripts of YouTube videos that I've done, you name it, and I said, "Hey, distill this into a brand voice skill." So it broke down the way that I talk, the way that I write, so that it feels natural.

Skill 2: Conversion-Focused Landing Page Architecture

I use the same architecture that Claude Code was able to reference on each and every page using my voice.

I rebuilt my entire website using this, and it's been working pretty well. So definitely leverage skills. And with the tool use and the context ability of 4.5, it's going to do a really good job with those. So I boiled all that down also into like a landing page architecture that I utilize. So I've been pumping out a lot of landing pages on my website lately. We've been doing these workshops. I wanted to create like a lead magnet around those so that I could gather emails. I wanted to redesign the homepage, and I use the same architecture that Claude Code was able to reference on each and every page using my voice.

This is sort of an overview of the architecture that I use and probably a lot of other people use whether they know it or not. So, we want to have like an impactful hero section. What is this getting you? What's sort of the transformation or the outcome? We go through the problem agitate phase. So this is sort of like what's the issue you're facing? How do you stoke the pain to make it feel like you really need something? And then you're coming in with a solution. So problem-agitate-solution is kind of a classic framework for conversion. We're providing the solution with this like value stack. Took that from sort of studying Hormozi's stuff where we're trying to make it feel like we're giving you so much value that it feels dumb to say no, right? And then we follow up with social proof, the transformation, kind of backing up and reselling this sort of major outcome that you're going to get, having a secondary strong CTA, and then, you know, if you need like a footer or anything like that.

PRO TIP: The Boring Stuff Pays Dividends

Do the research up front, set up the skills (Voice Skill + Architecture Skill), throw one prompt into the system, and you'll get a great result. Doing the research and building these skills out (maybe you have two or three) and then attacking the project with just one clear prompt can get you a long way.

Skill 3: The Front-