This is discussed a lot on the board. Not at all being "snarky", but I would definitely recommend doing a quick search for "Water park" or Typhoon Lagoon or Blizzard Beach. You'll find tons of info. Cliff notes....
Many water park veterans like myself say it's pretty much 50/50. We've been to each one more times than I can remember. BB has a better "organized" kids area called Ski Patrol, which is fun for kids ages 4-10. However, TL also has a fun kids area. TL also has a far better wave pool and some pretty cool slides. So it really is 50/50.