Well, both parks are kind of a mix depending on what you want to do....
I think the lazy river at BB has more shade but if you are going to be at the top of the mountain doing slides and stuff for a while there is basically zero shade up there.....
At TL there are plenty of out of the way "coves" that have a sandy area, bunches of trees and free pavilions. The only drawback is that they are far from the wave pool and you have to be there early. My family gets to TL and we hurry to the back right corner and make a claim on some chairs in the the pavilion near Shark reef. We have 5 in our family and we never have a problem claiming a small section under the pavilion by just laying our towels out on our chairs. One year we found a South American tour group had over-run our chairs but we asked them to move and they did. It really wasn't that big of a deal and we have not had any other issues. It is very close to shark reef, the place that does the pearls and a nice food stand with picnic tables. I think there are about 4-5 free pavilions just in that area with more around the park. Also very close to one of the many entry points to the lazy river....
From what I remember the BB reserved umbrella area is tucked away in a quite cove. TL's umbrellas are along the side of wave pool.