South and John Snow are really similar in terms of facilities and accommodation. If you're worried about how established it is, John Snow has a much longer history, its just that its changed the location of its accom permanently after the site was finished. South and John Snow do share the Hub which is where gowned formals are held, but your overall decision will depend on how much you want tradition as part of your college life. Also remember that your college allocation is based on ranks, so I'd recommended putting both of these in your top few if you're looking for self catered and owned.