This is asked a lot, and the answer really is 50/50. We love them both, almost exactly equally. They have a lot of similarities. But some key differences....
The biggest difference is the wave pool. The one at TL is like nothing you've probably seen. The waves are HUGE, as in you need to be a strong swimmer to be in the deep part of it. If you're not a strong swimmer, no problem, just stay in the shallow area. But the waves are massive and come once every 90 seconds or 2 minutes. We love it. The wave pool in BB is far calmer...they are continuous but gentle waves. They're gentle enough that they have inner tubes you can float in. I like it, but frankly it makes me sea sick after a little while.
TL has Crush n Gusher, a "roller coaster" style tube slide. A jet of water pushes you up some small inclines, so it's not just downhill. BB doesn't have this.
The family tube at BB can hold 6 people, at TL it's only 4.
Both have great kid areas, but the one at BB has a zip line and an iceberg crossing game, meant for ages 4-9 roughly.
Both have big thrill slides. BB has Summit Plummet, and TL has Humunga Cowabunga. Very similar, though Summit is probably a bit bigger. BB also has Slush Gusher, which is a big slide with 2 "humps"...i.e. it goes down, levels off a bit, then drops, levels off, drops. The last drop you will catch air before landing back on the slide. Not much, but it feels like a lot.
Otherwise, a lot of similarities in the actual attractions...tube slides, body slides, lazy river, etc... Both have plenty of free shaded chairs for you to sit in. You don't need to show up 45 minutes before the park opens to get on good rides. Just show up 5 minutes early. For the first hour, you can ride anything you want with almost no wait. Just be prepared to climb stairs...lots and lots of stairs. BB has a ski lift style chair lift, but I'd caution against it, as it's got a long line and is slow. It stops very often because guests can't figure out how to get on/off.