Claude Code definitely has a head start, but there have been a few HN posts about a perceived nerfing of the intelligence and settings in the past month or so. Codex could capitalize on that weakness. They just introduced a $100 monthly 5x plan so they are at parity with the Claude Code plans. If Anthropic fiddles too much more with the settings then people will start to switch to Codex.
Codex is just better than Claude but Claude is faster and has the better UI for vscode. That’s why I use Claude as main coder with codex(5.4 with xhigh effort) as mcp reviewer etc. It is clear to me that codex is a better programmer but the UI and speed are too much of a con to use it exclusively. Claude is just clumsy