I use both at the same time:

- Claude Opus for general discussion, design, reviews, etc.

- Codex GPT-5.4 High for task breakdown and implementation.

I often feed their responses to each other (manual copy/paste) to validate/improve the design and/or implementation. The outcome has been better than using one alone.

This workflow keeps Claude's usage in check (it doesn't eat as much tokens), and leverages Codex generous usage limits. Although sometimes I run into Codex's weekly limit and I need to purchase additional credits: 1000 credits for $40, which last for another 4-5 days (which usually overlap with my weekly refresh, so not all the credits are used up).