Tough choice, but I'd go with TL. Though I love the slides at BB, you make up for them with them with the awesome Crush 'n' Gusher coaster slides. And then TL has the wave pool that BB cannot emulate. Could spend hours there. Sounds like the more "full day" plan to me.
My personal opinion is that Typhoon Lagoon has a more "relaxed" vibe, and typically, when I'm going to the water parks I want to get away from the hustle and bustle of the dry parks. So generally, Typhoon Lagoon would be my water park of choice.
When we were there in 2014, we asked the concierge desk at the Boardwalk which water park we should choose. We hadn't been to either park and my boys are not big coaster kids, they like the more mellow rides. He told us that TL would be better for us and it was perfect! We haven't done BB, but we did have a great time at TL and would go again.