Both cities have a lot of nightlife - you won't get bored.
Accommodation wise, Manchester probably has the biggest choice of accommodation of any university in the UK, and you are guaranteed a place even if you come through clearing.
Course - I can't help you with that, although I have heard that Manchester exclusively does one type of philosophy (I can't remember if it's continental or analytic though). Make sure you are happy with that.
I think Manchester's campus is pretty nice - green space, lots of new buildings, and the busiest bus route in Europe to take you to your halls.