I Tested Claude Sonnet 4.5 vs ChatGPT-5 vs Opus 4.1: The Results Will Surprise You

When Claude (Anthropic) released Sonnet 4.5 with the bold claim that it's "the best coding model in the world," I knew I had to put that statement to the test.

After all, ChatGPT-5 just dropped and made waves in the AI community. And Opus 4.1 has been the beloved king of coding AI for months now. Could this new Sonnet model really dethrone both of them?

I decided to run all three models through identical coding challenges to find out which one actually performs best in real-world scenarios. What I discovered changed my perspective on how we should think about "the best" AI coding assistant.

The Testing Methodology

To keep things fair, I gave each model the exact same prompts and challenges. No hand-holding, no tweaking between attempts (at least not initially). Just raw performance.

Here's what I tested:

Challenge 1: Game Development

I asked each model to create a fully functional Angry Birds game that works in the browser. The requirements were simple: make it fun, add animations, ensure it actually works, and make it visually appealing.

Challenge 2: Landing Page Design

I tasked each model with creating a professional landing page for email marketing agencies. The goal was conversion-focused design with proper copywriting, visual appeal, and adherence to existing brand guidelines.

The models had access to reference materials and could ask follow-up questions. I wanted to see how they handled complex, real-world tasks that developers and designers face daily.

Round 1: The Angry Birds Challenge

Claude Sonnet 4.5: The Speed Demon That Crashed

Sonnet 4.5 finished first. We're talking about a minute or so compared to 5-10 minutes for the others. Impressive, right?

Not so fast.

When I opened the game, it looked visually appealing at first glance. Good graphics, nice layout. But the moment I tried to play, everything fell apart.

The slingshot mechanics were completely broken. I couldn't pull back properly. The bird barely flew. And when I inevitably lost, the game crashed entirely. There was no way to restart without refreshing the entire page.

It was essentially unplayable.

Verdict: Beautiful but broken.

Claude Opus 4.1: The Unexpected Champion

Opus 4.1 took longer to generate the code, but the difference in output quality was night and day.

First, it gave me an actual entry screen with instructions on how to play. Nice touch.

When I clicked "Play Game," the mechanics worked perfectly. The slingshot responded smoothly. The physics felt right. The collision detection was accurate. Most importantly, it was actually fun to play.

I found myself going through multiple levels, genuinely enjoying the experience. For a first attempt at creating a game from a simple prompt, this was remarkably good.

Verdict: Opus crushed this challenge.

ChatGPT-5: The Confusing Mess

ChatGPT-5 took the longest to generate the code. When it finally finished, I opened what it called "Slingbirds."

I honestly couldn't figure out what I was supposed to do. The interface was confusing. There seemed to be some bowling-like mechanics? The birds weren't even visible. I clicked around trying to make sense of it, but the game was essentially non-functional.

Verdict: Not even in the running.

Round 2: Second Chances

I'm not one to judge based on a single attempt. Maybe Sonnet 4.5 just had a bad day. I gave all the models another shot with slightly refined prompts.

Sonnet 4.5: Still Struggling

The second attempt from Sonnet 4.5 was marginally better. The game loaded, and I could see some improvements in the interface. But the physics were still fundamentally broken. The bird movement felt wrong, and the gameplay experience was frustrating rather than fun.

ChatGPT-5: Even Worse

Somehow, ChatGPT-5's second attempt was even more confusing than the first. The output was bad enough that I decided not to waste more time on it.

Opus 4.1: Consistent Excellence

I didn't even bother testing Opus 4.1 again for the game. It already worked perfectly.

The Ultra Think Experiment

Claude's models have a feature called "extended thinking" or "ultra think" mode. I decided to give Sonnet 4.5 one final chance with this feature enabled, thinking maybe it just needed more processing time to really nail the challenge.

The result? Almost equally as bad as the first attempt.

This got me thinking: maybe Sonnet 4.5 requires extremely specific, well-crafted prompts to perform well. Meanwhile, Opus 4.1 seems to handle vaguer instructions and still deliver quality results.

Challenge 2: Landing Page Design

This is where things got interesting.

I asked all three models to create a conversion-focused landing page for email marketing agencies. They had access to my company's existing website, brand guidelines, and documentation. The goal was to create something that looked professional, matched our design system, and would actually convert visitors into leads.

The Results Were Surprising

Without revealing which model created which page initially (I wanted to evaluate them blindly), here's what I found:

Page 1: Clean but Generic This landing page looked professional but felt a bit cookie-cutter. The copy was decent, but nothing special. It hit all the basic points but lacked personality. The visual design was safe.

Page 2: Inconsistent but Ambitious This page tried to do a lot. Some sections were excellent, others felt off-brand. The color choices were questionable in places, making some text hard to read. It needed several rounds of iteration to fix readability issues.

Page 3: Consistent and Conversion-Focused This page immediately stood out for its design consistency. It maintained our brand standards throughout, used whitespace effectively, and the copywriting was sharp. The FAQ section asked exactly the right questions that potential clients would have. The overall structure made sense from a conversion perspective.

The Big Reveal

• Page 1 was ChatGPT-5. Solid, but nothing spectacular.
• Page 2 was Opus 4.1. Ambitious but needed work.
• Page 3 was Sonnet 4.5. It absolutely nailed this challenge.

Testing Round 2: A Fresh Start

To make sure the landing page results weren't influenced by the models looking at each other's work, I started a completely fresh chat and asked Sonnet 4.5 to create a landing page for Facebook ads agencies instead.

The results were impressive again. Sonnet 4.5 showed strong consistency in design, made fewer errors overall, and understood the conversion optimization requirements well.

Yes, it messed up some color choices initially that made text unreadable. And yes, it took 3-4 rounds of feedback to get everything right. But the final output was genuinely good.

The structure, the visual hierarchy, the choice to use fewer words but make each one count – it all worked together cohesively.

What I Learned: There Is No "Best" AI Model

Here's my honest take after spending hours testing these models:

Claude Opus 4.1 excels at:

• Creative problem-solving
• Game development and complex logic
• Handling vague or imperfect prompts
• Getting things right on the first try

Claude Sonnet 4.5 excels at:

• Structured design tasks
• Consistency and attention to detail
• Landing pages and web design
• Following established patterns

ChatGPT-5 excels at:

• Well... I'm still figuring that one out based on these tests

The claim that Sonnet 4.5 is "the best coding model in the world" is both true and misleading. It depends entirely on what you're building.

For web design, landing pages, and tasks that require strict adherence to design systems, Sonnet 4.5 is excellent. For creative problem-solving, game development, and tasks that need intuition with imperfect instructions, Opus 4.1 is still the champion.

The Prompt Quality Factor

One pattern I noticed: Sonnet 4.5 seems to require more specific, detailed prompts to perform at its peak. When I gave it precise instructions and clear references, it delivered outstanding results.

Opus 4.1, on the other hand, performed well even with my somewhat vague initial prompts. It filled in the gaps intelligently and made good assumptions about what I wanted.

This isn't necessarily a weakness of Sonnet 4.5. It might just mean it's optimized differently. If you're willing to invest time in crafting detailed prompts, Sonnet 4.5 can deliver remarkably consistent output.

What About the Other Updates?

Claude also released some other interesting updates alongside Sonnet 4.5 that I didn't cover in detail:

Claude Agent SDK – This looks promising for building autonomous agent systems. I'm curious how it compares to what you can build with tools like N8N.

Imagine With Claude – This appears to be Claude's answer to platforms like Lovable, Bolt, and V0. It's essentially an AI-powered app builder. I'm planning to test this in a future comparison.

The ChatGPT-5 Phenomenon

Remember when ChatGPT-5 first launched and everyone complained it wasn't as good as expected? Then two weeks later, it was actually performing really well?

I think we might be seeing something similar with Sonnet 4.5. The model might need time to settle, or maybe we all need time to learn how to prompt it effectively.

I'll definitely be spending more time with Sonnet 4.5 to see if my results improve as I learn its strengths and weaknesses.

Final Verdict

If you forced me to pick one model for all my coding tasks, I'd still go with Opus 4.1. It's the most versatile and handles the widest variety of tasks well.

But for specific use cases like landing page design, Sonnet 4.5 is now my go-to. The consistency and attention to design details make it worth using for those particular tasks.

As for ChatGPT-5, I need to test it more in different scenarios. These particular challenges didn't play to its strengths, whatever those might be.

What's Your Experience?

I'm curious to hear from others who have tested these models. Are you seeing similar results? Have you found use cases where Sonnet 4.5 truly shines?

Drop your thoughts in the comments on the video, and let me know what you'd like to see tested next.

Watch the full testing process here: https://youtu.be/TAGUl0Xj7xg

The video shows every attempt, every failure, and all the iterations in real-time. If you're making decisions about which AI coding assistant to use for your projects, it's worth watching the whole thing.

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#ai #claude #chatgpt #opus #coding #programming #webdev #comparison #testing #automation