Typhoon Lagoon is the best water park on the planet! It is absolutely beautiful with all the lush greenery, the excellent themeing and all of the elaborate props found throughout. Additionally, it has some excellent rides. Far superior to any non-Disney water park hands down. And the selection of rides really spans all tastes. There's something for everyone.
Blizzard Beach has got the most thrilling rides. Although Typhoon Lagoon is my absolute favorite, if my goal were simply to do nothing but go on fast water slides all day nonstop (as is often the case with teenage boys), then I would probably be more impressed with Blizzard Beach. Although the themeing with Blizzard Beach was very creative, I think the one thing they forgot to consider was the fact that although it may LOOK like snow and ice, it is in reality hot concrete that is blinding white. And for some reason, shade was not factored in when building Blizzard Beach. So it is someone uncomfortable. They seemed to have more of a shortage of lounge chairs too when I was there.
So for simply pure thrills and if you don't plan to do any relaxing or enjoying the the beauty: Blizzard Beach
For the overall experience AND excellent thrills: Typhoon Lagoon