I have stayed at both and agree that you have to decide what you want for this vacation. BLT Lake view rooms are so nice, and the view of the fireworks from the top floor is fun, esp just returning to your room on the elevator when they end. It would be nice to be on the Monorail, you have so many dining options. And at a hot time of year the air conditioning is a plus. If you are spending a lot of time at the MK then BLT wins for convenience, although the boat ride to WL is nice.
WL is so beautiful, much more so that BLT. The pool area is nice at WL, with the villa pool being esp quiet. I have stayed once in the villas, and really did not get a great location. First floor at the end of a very long hall, furthest from the lobby. With my 80's plus y/o Mom it was a haul. No view at all from the room. I loved the tour of the Lodge, the bike rental which I took through Fort Wilderness, and just relaxing in the large beautiful lobby. It was much more convenient to have my car at BLT, parking was so easy and close, WL not so much.
I would stay at either place again, they are both great resorts!