I don't have a preference; I play with both Russian and English maps, the main thing is that the map is interesting. By the way, sometimes there are differences between them. In the map "Besonnitsa," unlike its English version "Insomnia," blue is the ally. This might be observed in other maps as well.

I played German maps, but I couldn't understand the descriptions :D, but I still beat the AI without knowing the language. I haven't tried Chinese maps much yet; I downloaded a couple of maps but haven't decided yet, based on the stories about how difficult they are.