Can't tell you anything about Wadham, but I went to St John's with my college earlier this year and stayed overnight, and liked it so much that it's made me change my mind and decide to apply to Oxford =) I kinda get what you mean about it seeming a little bit dry and cold, but when we were talking to some of the students it sounds like they have looooooads of stuff to get involved in ther (apparently they have really really good music and drama societies), and all the students seemed like really lovely people. Plus St John's are the richest and can give you oodles of financial support, so I don't know if that's something that'd affect your decision. And the accommodation there (although the buildings are mighty ugly) is very comfy =) dunno if I'm much help since I'm not already a student tehre, but I really absolutely loved St John's ^_^ and I was also swayed by the fact that they have an active music society and good facilities. And their library is gorgeous <3