Both are good! Bournmouth is better if you like the seaside. Bristol is a very large city. It is easy to get a train from both places to other towns in the country. Brisol is next to Bath which is one of most beutiful cities in the county. If you want a historical day out, visit the Roman Bath's in Bath, they are really amazing!. Both have universities so there are lots of young people, clubs, bars attractions ect.

Hmm, it's really hard to choose! It's really up to you!

Personally I'd choose Bounemouth as it should be a great time to be near the beach. Of course I think Bristol is best if you like cathedrals and old architecture. 

Thank you :)

Thank you George!