A couple of points:
just because there are a good number of MMLers doesn't necessarily mean a great community - we are all split off into different languages/options so can go the entire 4 years never doing the same subjects!! Any 'community' is made by the students there at the time - make the effort, make the community
OP if you are studying Russian I would do some research and find colleges with fellows in Russian - they tend to have a far higher proportion of Russianists (although of course we can't tell whether this is because lots of people think like this or because they like to accept Russianists). For example, in my college (Sidney) typically 2 or 3 out of the 6 or so in each year have Russian. Off the top of my head Jesus and Trinity, also Clare and a few others that I can't remember have decent proportions of Russianists. However, don't take my word for it - do some more research if this is your main criterion!
For MML (except for first year French and other really big languages) all of the teaching is organised centrally so college doesn't make a huge amount of difference.
Generally college choice boils down to size, location and any weird facilities/architecture you want. Think about whether you want to be close to lectures or to the centre of town. If in doubt, try to get to Cam and have a wander round colleges - if anyone tries to charge you as a tourist just say you are a prospective student and they will be nice to you. If they aren't then cross them off your list!!
I would also echo Tortious' comment about Corpus - it is a lovely college but it is absolutely tiny. If this is right for you then great but think about it!