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The short answer
Claude for real projects — it reasons across many files more reliably, and Claude Code is the more mature terminal agent.
Tie on isolated snippets. If you mostly ask for single functions, pick on price or whichever interface you prefer, because the code will be equivalent.
| Task | Winner | Why |
|---|---|---|
| Single functions, snippets | Tie | Both consistently correct |
| Multi-file reasoning | Claude | Holds the whole project in view |
| Large refactors | Claude | Catches more knock-on changes |
| Debugging without a stack trace | Claude | Flags uncertainty instead of guessing |
| Learning to code | ChatGPT | Gentler explanations, more material online |
| Data analysis scripts | ChatGPT | Runs code and charts results inline |
Snippets: genuinely a tie
Write a debounce function. Parse this date format. Give me a regex for UK postcodes. Both tools handle these correctly and have for a long time.
Comparisons that benchmark this and declare a winner are measuring noise. If this is the bulk of your use, the choice does not matter much — pick on the rest of the feature set.
Real codebases: Claude
Here is the task that separates them: twelve files, and the checkout breaks when a discount code is applied to a basket containing a subscription item.
Solving that requires tracing what calls what and noticing that two modules make incompatible assumptions about the same data. Claude is consistently better at this — it is the difference between a tool that answers questions about code and one that reasons about a system.
The same gap shows in refactoring. Ask for a change touching eight files and Claude is more likely to catch the seventh and eighth.
Debugging: Claude, slightly
With a stack trace, both are good. Without one — wrong output, no error, no obvious cause — they diverge.
Claude is more willing to say what it is uncertain about and propose how to narrow it down. ChatGPT more often produces a single confident explanation, which is excellent when right and costs you an hour when wrong.
For debugging specifically, "it is probably one of these three things, add a log here to find out" beats a decisive guess.
Terminal agents
Both offer agents that work directly in your environment rather than a chat window: Claude Code and Codex.
This matters more than it sounds, because copy-pasting between a browser and an editor is where most of the friction in AI-assisted coding lives. Claude Code has been at it longer and is the more mature product; Codex is improving quickly.
Either way, the agent is included with the subscription — if you pay for one of these already, use the agent rather than the chat window.
Where ChatGPT wins
Learning. If you are new to programming, ChatGPT's explanations are gentler and there is far more community material about using it.
Data work. Upload a spreadsheet, ask questions in plain English, get charts back. It writes and runs the code itself. For analysis scripts this is a real advantage.
Common questions
Which AI writes better code?
Is Claude Code better than Codex?
Should I pay for both?
Do these tools write correct code?
Test on your own codebase
Both have free tiers. Give each the same real bug from your actual project — that comparison tells you more than any benchmark.