Hello from WDW! We are currently here and have done both TL and BB in the past two weeks with our kids (2 and 5). In my opinion, each park's kiddie area caters to a slightly different type of kid. The TL kiddie area has lots of spraying things - to the point where you cannot help but get squirted. My kids did not enjoy that. They did however love the gentle tube ride they offer. Little kids pretty much cannot use the wave pool - way too strong, but the little tubes they provide that are "hole" less are wonderful in the lazy river. The family raft ride is very short and has quite a few sharp "bumps" and lots of water crashing in on you. My kids had a wonderful time here, and I absolutely love the theming.
At BB, there is a pool with a zero depth entry and much less constant spraying. There are little people slides that keep the kids running back for more. My 5 year old actually really liked the preteen area too! Well, even the two year old was loving the tube ride. The 5 year old was thrilled with the iceberg walk and the hanging drop (handle bar on a pulley system). I was surprised! The lazy river is great, but no "hole" less tubes. The family raft ride was the best! It was much longer, less water pouring in on you from above and very little harsh bumps! The two year old kept wanting to go again and again! Oh, and the wave pool is more "typical", with tubes provided to float. My two year old fell asleep with his dad. Great memories.
So, in my opinion. If you have a son who loves the squirting and pouring water then TL is for you. If your kids need a bit less intensity, then BB is the place. Don't think BB isn't amazing it is! In fact, after being a real fan of TL, I think we have a new favorite!
Good Luck!