I had this same choice. I chose Nottingham because I wanted a campus university experience and Nottingham's campus is one of the best campuses you'll find. With Bristol there didn't seem to be much of a centre to it, just the impression I got. Both very well respected and nice unis so I doubt you can go wrong.
They're on the same sort of level reputation/career prospect wise. Bristol probably edges it nowadays with Notts dropping in rankings, but that wasnt the case a few years back, and the difference is certainly not enough to make it a factor when choosing. Therefore it comes down to which one you prefer, and which course is better. I rejected Bristol for Notts BTW, cos for me the campus environment, social life, and course seemed better. Visit both, really analyse their courses, and see which you think is better