We went to both last June with kids who were 9, 5, and 2 at the time, and we preferred BB.
BB has a preschool area (which was great for the 2 almost 3 year old) and of some interest to our 5 year old. The 5 year old also went on many of the 'adult' rides.....any that didn't require swimming at the bottom. They also have a 'Junior Ski-Patrol' area which is supposed to be targeted to 5-12 year olds; that'd be a great option for anybody who doesn't meet the height requirements on the 'adult' ride. Finally, the family raft ride is the best!
TL has incredibly nice landscaping and a fantastic wave pool. Also lots of sand if that appeals to your kids. However, my older kids weren't as thrilled with the water slides there. My biggest complaint was that the baby/preschool area in TL has lots of water spraying from above, and my 2 year old (who was actually 3 months away from being 3) hated that. We had to work hard to find a place where he could stand without having water coming down on him--slides and play areas alike. They also have a pirate ship in the middle that enables kids to direct water cannons.....fun for the kids pointing them, but not much fun for some of the toddler/preschooler targets! Seemed like most of the preschool slides at BB didn't have the 'water spraying from above' set-up.
Both parks are fun.....it's great if you can do both....but with young kids or varied age kids, we like BB best.