I went to Bristol and had an offer from durham but declined it. I would say the most important thing is what do you want out of your university experience, do you want to be in a vibrant city with a big night life scene with raves and night clubs, or do you want to go to a uni town for a more intimate experience with social being dictated more by the activities your college provides. If I could do it again I would rather have gone to durham just because I think now as a graduate I still have access to the vibrant life of a city as an adult and would have preferred to have a quieter uni experience with more formal and less of a heavy night life culture. I would also say depending on course durham is generally stronger reputation wise but they're both good unis so I don't think the difference is that significant.