Both TL and BB are great waterparks and you won't be dissaponted with either.
Typhoon Lagoon has more shade and the feel of a tropical Island, it has pretty good slides, the chance to snorkle with sharks (little ones) and other tropical fish at Shark Reef it also has the BEST wave pool.
BB, I agree with Rob, the themeing is clever, but it isn't as attractive (IMHO) as TL. Where BB scores is , without doubt, it's slides. There are more of them and they are definately "better" than those at TL. It's wave pool is good fun, but it's MUCH smaller than TL. BB also has, IMHO a slightly better "kids area"
Overall I think my preference is, just, TL although if thrill rides are a major issue that may tip it for BB.