It depends upon what you want.
The Tube slides at Typhoon Lagoon leave much to be desired as does the group slide. They are short, slow, and one of em is just plain bumpy and not all that much fun. The group slide made up a bit for it's short run by having a ton of wet features. You also have to roll your own tube up the stairs. The Storm slides (body slides) are worthy as is Humunga Kawabunga. The former are open and curvy. The latter straight and enclosed. Typhoon Lagoon has an awesome wave pool and a decent, but not great little kid's area. It also has the water coaster and the swim with the sharks. But to be honest, the view is superior and the wait non-existent to just view from the ship without snorkeling.
Blizzard Beach has a really nice group slide. It's long, and fun. It has two big thrill slides that Typhoon Lagoon doesn't have. It's tube slides are very fun and it also has the downhill tube racers which is set up like a side by side ski run. They also have the 8 lane head first mat slide which is also fun. They also have slalom slides that you go down head first on a mat. These were fun also. Blizzard Beach has a really nice bigger kids area as well as the little kids area. The Wave pool, leaves a bit to be desired. It's more of a relaxing gentle wave pool.
We found we did a lot more strenuous climbing at Blizzard beach than at Typhoon Lagoon. Also the queues were better themed at TL. At BB, several of the queues were just staircases. The slides themselves were well themed though.
All things considered, we preferred Blizzard beach simply because the tube slides and the group slide were so lacking at Typhoon Lagoon. Also, we have older kids now so the area for them at Blizzard Beach is a draw.