Academically there is any real difference between the two and whichever you choose it won't have any significant impact on your eventual Law career. So, its about Uni experience and what you want from that. They are very difference Universities - ie. Warwick isn't in Warwick. Its on an isolated campus site near Coventry, and Bristol is a city campus in an interesting city with lots to do. Where are you going to feel most comfortable?
Both Unis will invite you to offer-holder visit days in the spring term and this is a good opportunity to take a more critical look around and talk to current students. And remember that have until May to make this decision, and there is no advantage in making an earlier decision, so sit on your hands, and do some calm and careful thinking first.