I'm thinking of switching to Grok on Cursor (purely for $$ reasons). But Opus >= 4.8 has been fantastic; it's hard to leave, even just to dabble with other models.
Codex 5.6 sol is arguably superior to Claude, albeit very close. They're functionally indistinguishable to me, but if you're concerned about $$, Codex gives you much, much more bang for your buck.
I've been using Grok instead of Opus the past few weeks.
It's a downgrade, but barely noticeable for me and totally inconsequential for the amount of work required to fix it and the corresponding $$$ saving.