My wife and I went to Blizzard Beach this past June (and had a great time!). Some of the smaller rides were walk-ups. The Downhill Double Dipper was probably the longest line we waited in, which was roughly 45 minutes. The other two "purple slope" rides were anyplace from walk-up to 10 minutes most of the day.
The Slush Gusher (and Summit Plummet) were both close to 45 minutes, but after the intense "personal" pain we both experienced on Slush Gusher, there was no interest in going on the other.
This was my first experience at a water park, and I loved it. We'll definitely be adding a trip to it or Typhoon Lagoon to our vacation plans from now on.
Depends on what time you're planning on going to them. BB is probably more popular than TL because of Summit Plummit (which is a very popular slide). And it depends on what time of year you go. They won't be open in mid-late Fall, Winter, and early-mid Spring, so if you go in late Spring when it's still school time for kids they will probably be half empty, or in other cases nearly deserted. It gets really busy in the summer for very obvious reasons, but they're both equally popular for two completely different things, so if you go to BB you'll get very long lines on Summit Plummit, and if you go to TL you'll find that the wave pool will be packed with people. So, you know, it all depends on very basic things.
I'm Silver. And I've been a Mouseketeer since 1994!