Opus 4.8 and Opus 5 have been much better than Gemini Pro hands down. Fable is miles ahead, it can look at Opus output and break out of the mold of limited closed minded thinking. Opus will say these are the 3 choices and Fable will be like nah, you have another choice and Fable is always the better choice over Opus 5. Fable also knows when to stop which further highlights why it is better for planning.
Opus 5 likes to do way more than needed and forget your CLAUDE.md exists, it's annoying. It was a problem in Opus 4.8, but it just goes further ahead than you intended and usually you have to backtrack because it did things you did not ask for. This kind of eagerness can be helpful to non coders i guess, but not for me.
Gemini Pro has fallen behind... Flash is great as a sub agent though. Incredible accuracy at fast speed and cheap cost.