Does it matter which college I apply to?

The short answer is no, not really. 

Each colllege is different - the number of students in each year group, whether it's old or new, whether it's central or slightly outside of town.

But that said, you will receive the same tuition no matter which college you end up at and everyone ends up loving the college they get (and if you don't, you can apply to transfer colleges).

It's more worth your time to spend your application really thinking about your subject, than spending time agonising over which college you want to apply to. Think about some key factors like size of year group, what kind of architecture you like, to decide which college you want to go to, but it's not worth trying to game the system by applying to one college over another because they received fewer applications last year for example.

The Oxbridge winter and summer "pool" system means that if a college thinks you deserve to study here, even if they don't have a place for you at their college, they will put your application into the pool so that other colleges can offer you a place. About 1 in 5 students get pooled to a different college so try not get too attached to any one college!