Hi,
This is probably perfect for me as I'm from Bristol and study law at Exeter so should be able to help out.
Like others have said above, reputation and rankings really mean nothing. There's such a negligible difference between the two, that no employer is going to be bothered that you chose Exeter over Bristol or vice versa. International rankings also don't really mean much.
Taking rankings out of the equation, it sounds like Exeter is the better option. You've got a place there, it's campus like you seem to want, and it's more affordable. Getting into the LLB through clearing or adjustment with Bristol might not be easy either, especially with accommodation - I wouldn't be surprised if you're placed somewhere not very social.
Exeter is a great student city and I love it here; as for diversity, it's not very diverse, but I wouldn't say Bristol is the epitome of diversity either. As for things to do, Exeter has everything you need really, and that's coming from Bristol. I don't know what you planned to do, but nightlife is sufficient in Exeter, and most of it is to do with the people you're with more than anything.
Happy to answer anymore questions, but Exeter sounds like the much better, safer option.