That's been my experience as well switching from Opus to Codex. Reasoning takes longer but answers are precise. Claude is sloppy in comparison.

I started using Codex 5.3. Compare to Opus 4.6, it's more precise in pinning down bugs and more concise with code. Opus can be best described as distracted and easily agreeable. Codex actually digs deeper for root causes and push back when I'm wrong.

I'm going to test this on my kids.