Aurora, BB has a larger kiddie area. Tike's Peak (the BB area) has a general play area (shallow pool with props). There is a small kid only tube slide (very gentle -- and there is a lifeguard at both ends to help and assist the child). There is a pair of long slanted slides (which are best if the kids get a running start with because it's not very steep and the younger kids wind up just bouncing on their bums to go down). There is a smaller play area at the top with an icehouse theme and a very small slide too.
It doesn't sound like much but it's nicely done. It's also right across the teen area. There you will find a more daring tube slide but it is still quite tame (and yes your kids will be fine on it). Also the family raft slide at the top of the mountain may seem daunting but I see 2 year olds enjoy it all the time. And, of course you have the lazy river which is great for kids and the wave pool which does NOT break into big waves. Just small beachlike bobs.
Typhoon Lagoon is a much smaller park and you will also find it to be less crowded. Unfortunately the kid's area is a bit smaller, though marginally so. There is also a shallow water play area (with a tropical theme) and a small tube slide. Across from the Kethakiddie Creek play area for kids you have an inlet from the wave pool with two small water slides for kids. It's a nice touch that you won't find at BB. This wave pool is more intense with actual segments of larger waves -- just don't go out too deep and the kids will be fine.
So, for kids, I'm tempted to say that it's almost a toss-up. If your kids were older BB has far more slides. If your kids were adults, TL has the cool snorkeling reef (which any kid can do actually -- though it helps if they know how to snorkel, which is probably a bit much to ask of a 4 and a 5 year old, but, you never know -- my 9 year old has been snorkeling since he was 3).
I guess BB is only marginally better, but because it will be the more crowded of the two, you can't go wrong with either one. If one is closer to your hotel go with that one. And don't forget the sunblock!
