This is truly a 50/50 thing, IMO. They're both fabulous for kids. BB does have Ski Patrol, which is right in the wheelhouse of a 7 year old. It also has Summit Plummet and Slush Gusher if your DD is adventurous. However, its' wave pool pales in comparison to TL. It's amazing. And you don't need to go into the deep end if your DD isn't a strong swimmer, it's a zero entry so you can go as shallow as you'd like. It's no more dangerous than the wave pool at BB...in fact in spots I'd argue that it's even less "dangerous". It also has Crush Gusher, which is unique to TL and lots of fun. It also has a higher capacity on it's "big" slide, Humunga Kowabunga (3 vs 1 at a time at BB Summit Plummet). They both have great family tube rides and lazy rivers.
You won't go wrong either way.