I have never stayed at BCV, but preferred view at BWV is any view that is not of the parking lot (Standard) or of the Boardwalk itself (Boardwalk view). It can be a view of either of the pools, the canal, or one of the "garden" areas.
Personally, I always try to get Standard view.. It takes less points...
I think the bigger question would be what type of ambiance do you want? BCV is more soothing.. BWV is more active...
The difference between each to Epcot/MGM is negligible..