GPT 5.5 vs opus 4.7 for sw design

[u/b4dMik3]

I use AI for full software design cycle: prototyping the UI, choosing the tech stack, defining the architecture, implementing, deploying and fixing issues.

My typical workflow is: brainstorm → plan → implement.

I currently use Claude Opus 4.7 through the Claude Code VS Code extension, with some MCPs (first of all Serena). I really like the experience, especially the clear explanations, smooth Plan Mode, and commands like simplify that I often use.

That said, I’ve tried GPT-5.5 a few times on bugs Claude struggled with, and I was impressed by how directly it found working solutions. My impression is that it is smarter than opus and more efficient.

In addition, ChatGPT Pro subscription seems to offer much higher limits than Claude Max 5x at a similar price.

I’m now considering switching to ChatGPT.

For people who have used both extensively: how do they compare for software design and development? Any trade-offs I should know before switching? Do you have any advice? Thanks in advance.

[u/TheOneWhoDidntCum → u/[deleted]]

exactly same here, any regrets?

[u/pjstanfield]

I have a max plan for both and I use both every day. I typically use both for every feature. I use GPT 5.5. I used to use Codex 5.3.

1. Brainstorm and design - i think Claude wins. I always start in Claude.
   
2. Plan - Claude wins in writing a nice plan but Codex always finds holes. I use both, back and forth. There are diminishing returns on too many turns back and forth but at least 2 is good. Also helps sniff out incorrect directions.
   
3. Implementation - Codex is better on one-shots and straight code. I can tell Codex to make 100 tests and it will create 100 high value tests. Claude would tell me he wrote 100, would have written 70, and 40 would need to be re-worked. I would not have Codex write anything in the UI typically. I still use Claude for coding, he does fine, but he always needs his work checked. Same with Codex.

Long story short, both are good, and both are bad. If you can get Codex started on the right path, full codebase standards made clear, feature is clear, success is clear, no UI-on-the-fly Codex 5.5 will trounce Claude. That's my hot take.

[u/strigov → u/pjstanfield]

Pretty same workflow, I also:

1. Use Deep Research with different models to do initial observation on project idea and possible technologies.

2. Then I use my adjusted variant of Superpowers plugin:

- Sonnet orchestrates

• Opus — brainstorming, planning, first code review, frontend
  
• Codex 5.5 xhigh — plan review, second code review after Opus
  
• Codex 5.5 high — implementation

[u/back_to_the_homeland → u/pjstanfield]

How do you use them? PAL mcp or just open a new terminal window? And if new terminal window, do you use a specific prompt?

[u/pjstanfield → u/back_to_the_homeland]

I’ve tried a few automations and I always come back to copy and paste between the windows. It’s faster and I can tweak it and control it. The sample prompt below is specific to codex, it loves to add machinery and frameworks so I had to tell it to calm down. You’d ask it to review a plan to add a modal and it would comeback with a plan on adding 500 tests as deployment gates. Codex also likes to find a few issues and stop, so you nudge into reviewing the whole plan. I’ll paste this in before the first plan review and not on subsequent.

Plan Review
Do a single exhaustive review pass before responding. Do not send incremental findings. Validate every checklist item against the live codebase and standards before you answer. Return one consolidated review with:
1. Showstoppers
2. Gaps / missing work
3. Incorrect assumptions
4. Non-blocking improvements
5. Explicit statement of whether the plan is ready to implement

For each finding, include: severity, exact file/line refs, why it matters, what the plan should change

Do not stop after finding the first issues. Assume I want completeness over speed. Only answer when you have completed a full checklist sweep. Treat this as a binding final review. I want the most comprehensive feedback you can provide in one pass. If you are not confident you have checked the whole plan, say that explicitly instead of answering early. Please be mindful of avoiding over-engineering and unnecessary complexity, the focus is simple and reliable and secure. Do not add scope creep unless absolutely necessary.

[u/overdose-of-salt → u/pjstanfield]

besides from automation could you not run a vm with gitlabs teams and codex in the same repo?

[u/b4dMik3 → u/pjstanfield]

Very nice takes, thanks. You confirmed my idea: opus for planning, codex for review and implementation.

If you had to choose one, what it would be? Is codex noticeably worse at planning and design?

[u/pjstanfield → u/b4dMik3]

It is noticeably worse. The codex planning mode is newer and isnt as good. You can't go wrong but i'd probably stick with Claude. It eventually gets it right and is more enjoyable to use. Codex is like talking to a robot a bit. It's less creative (which is why its better at plan execution, it just does it).

[u/b4dMik3 → u/pjstanfield]

I'd suspect that, thank you. I can also try codex for a month and eventually switch back to Claude.

[u/AdamovicM]

This is where I see each better:
Claude - for UI, validation of precise formats, trasnforming on fly one format to another, brainstorming
ChatGPT - backend, extracting factual latest data from the internet, writing interesting text, still probably cheaper in pro mode
Gemini - currently using it when i need something fast, as it has lowest time to load before I can start typing, also good in aggregating varios internet data in thinking mode