Well, you're going to get a lot of varying answers to #1 since it's such a subjective question. The main attraction at Typhoon Lagoon is the wave pool which sends 6 foot waves out every few minutes. TL also has a snorkling area called Shark Reef where you can, literally, swim with sharks.
Blizzard Beach is more known for its enromous water slides.
Aside from those two items, both have a plethora of individual attractions. Both have areas especially for young children, family raft rides, water slides, etc.
More people tend to favor Blizzard Beach, but I've never been disappointed with Typhoon Lagoon myself. Take a look at the park descriptions and judge for yourself. Either way I doubt you'll regret your decision.
Both parks do rent towels for $1, but you are welcome to bring your own and save a few bucks.