Blizzard Beach is best overall for teens, more slides.
BUT, the new Crush 'n' Gusher at TL uses the Master Blaster technology, and is not to be missed. It's like a water roller coaster, where blasts of water actually shoot you uphill.
Keep in mind that one day at one water park is around $37. For only $12 more, you can add the four plus option to your MYW base tickets, which you can also use for PI or DisneyQuest.