Even those who have zero experience with different (human) languages could've known this if they liked, from the fact that on the LMArena leaderboards, Gemini models have consistently ranked much higher in non-English languages than in English. This gap has actually shrunk a lot over time! In the 1.5 Pro days this advantage was huge, it would be like 10th in English and 2nd in many other languages.
Nevertheless, it still depends on the specific language you're targeting. Gemini isn't the winner on every single one of them. If you're only going to choose one model for use with many languages, it should be Gemini. But if the set of languages isn't too large, optimizing model selection per language is worth it.