I'm a Blizzard Beach fan all the way!
my family and I have been to both waterparks numerous times and Blizzard Beach is way nicer. I'm 18 and my two younger brothers who are 12 and 16 all enjoy the rides BB has to offer much better. Blizzard Beach has a greater variety of slides including fast plungers like Summit Plummit and Slusher Gusher, Tube Slides with fun twists and Turns including the Downhill Double Dipper (along with the one of the worlds largest family raft rides), and in my opinion the best attraction of all the Toboggan Racers.
The only thing that's nicer about Typhoon Lagoon is the tidle wave pool which has really strong currents. Although BB has one too, its currents aren't quite as strong though. The slides and other attractions at TL were weak and not too fun. The Shark reef TL offers is really neat and if your children aren't too afraid of sharks it's a really cool experience.
If your choosing between the two my vote defintly goes to Blizzard Beach!