Tough choice for sure. They both have their strong points and are very different for atmosphere.
Here are my thoughts:
VWL: The theme is great. We find ourselves walking around there with our mouths open and our heads on swivels. It hasn't gotten old. Since we have purchased there, we have stayed for 25+ nights over several trips and we still are impressed everytime we go back. We are from NH and we thought that if we wanted to see trees and that type theme we could see it up here. We were wrong. The theme is so impressive. Prior to our first visit, my wife was a bit reluctant and didn't think she would be thrilled. Within 20 minutes of being there she was taken back by it. We initially wanted a Florida-type theme with the bright colors and palm trees. The location: If you love MK, you will love the location of VWL. The boat is a quick hop right to the park. If you want to go to Epcot, hop on the monorail. We don't regret the choice. We added on again while we were there in August.
BCV: I can't wait to be able to comment on the stay there. We walked and saw as much as we could from the outside during our stay in February and it looks like it will be really nice. The theme is nice and the SAB is pretty cool. The location is awesome if you are a big Epcot fan. IMHO you have the benefit of being close to the boardwalk, but perhaps removed from the noise a bit. I could be wrong, but just an observation. We are excited for it. We did an add on there too.

We originally wanted to get in on BWV but missed out. We wanted the option of the MK and Epcot location. We waited for it to open so we could have the location.
If I could only choose one based on theme, I think it would be hard, though I may lean towards VWL. HOWEVER, if you are really torn, I would base my decision on which location I like better. If you want to be by MK, then you would wish you bought at VWL and visa versa. I think that either one you choose, you can't go wrong.
Another thought: based on the points you plan to purchase, split between them both.
As always, good luck ad have fun!