I went open application (and I think a good number of TSRers did), was totally fine. (well I'm not there but it seems like the one for me)
You may want to think about a few main things that are not an opinion or like, and you may not be able to get at some colleges.
Self-catered, fully catered, or half-catered(I'm not sure which meals this is)?
Ensuite or not?
Shared bedroom or not? (though so many are shared this may be fussy and you probably learn to be happy with it or only share 1 term out of 3).
I can't think of anything else that would avoid doing open application.
Old building or new - bah all are up to date and you only have to walk down the road to see a world heritage site.
Location - all are near enough to walk to the centre and lectures, even I will end up loving the gradients (I hope).
Sport - all I get from that is that every college is great and unique for it, same with friendliness, music, and such.