Blizzard Beach has great tube slides, etc., and we liked it a ton, but my family all agreed that Typhoon Lagoon was our favorite. I personally love the wave pool (I know many out there despise the risk of getting scraped up, but I just love how you hear that big "boom" when the wave comes out and everyone screams with excitement!) I like the tropical feel at TL better than the white-out scenery of BB.
That said, my 4-yr-old DS hasn't stopped talking about the "family raft ride" (Teamboat Springs, I think) at Blizzard Beach. It is great...short wait time to get on and the ride goes on forever!
BB definitely feels more crowded.