My take has been...

Gemini 3.1 (and Gemini 3) are a lot smarter than Claude Opus 4.6

But...

Gemini 3 series are both mediocre at best in agentic coding.

Single shot question(s) about a code problem vs "build this feature autonomously".

Gemini's CLI harness is just not very good and Gemini's approach to agentic coding leaves a lot to be desired. It doesn't perform the double-checking that Codex does, it's slower than Claude, it runs off and does things without asking and not clearly explaining why.