What an interesting time to post a question...
I don't know much about the other 3, but I can tell you a few things about John's.
1. 2/3 share rooms, but if you're adamant about not sharing it, you can usually get a single by giving a decent reason
pro: location near durham city, near cathedral, near castle, near law/history departments, best food in the university, small/tight community, best/one of the best bars, old/historical college
con: far from science sites, might have to share, small (if it's a con for you), small gym, few organized entertainment events