Between codex and Claude code, I am using both on two entirely different projects, so it's not a fair comparison, but the two things Claude has in my unscientific testing is a better plan mode (though having to use the magic password ultrathink belies needing to learn how to prompt it properly) resulting in a better and longer Todo.md (but again, the two projects between the two are very different, so don't consider it a scientific comparison). The other thing that Claude code has that codex does not is a more advanced ability to run things in the background, both as in "npm run dev"/other webserver in the background and being able to run curl/whatever against it, and gather logs from the webserver, error message or otherwise. The other thing is Claude code can be told to run things "in sub-agents" and work on multiple things simultaneously. If there is a way to get codex to do it, it won't tell me and says it can't do that. Not that I necessarily believe it. My experience with codex is that, despite instructions in agents.md, it'll forget and get its wires crossed. I'm using --model gpt-5-codex, and codex reports version 0.42.0.