hey there, final year undergrad here. sorry for the late reply; hope it’s still useful!
I’m not really sure I get your line of reasoning tbh - to me it feels like it could very well be easier to make friends at smaller/ less-central or even grad-only colleges, with tighter-knit communities and all that. also, from what I’ve heard from grad friends, while people are generally lovely and friendly, there’s no way of telling what kind of housemates/ hall-mates you’ll happen to get regardless of which college you’re in. and formal halls (and May Balls and the like) are pretty amazing, but again (at least in my experience), it isn’t so much about your own college’s formal halls but going to formals at friends’ colleges (I *have* heard a lot about Caius’s grad superhalls (http://www.mcr.cai.cam.ac.uk/?page_id=31) though!)
– so while I think that more information can’t hurt and that your picks sound good, imho probably the best way to be sure you make friends isn’t so much hoping you get lucky with housing allocations, but via societies like the Corpus Playroom and St John’s Picturehouse, or if you’re willing casual college-level sports like lacrosse, badminton and of course rowing
