The truth is that they are very, very similar. The room sizes are very close, close enough that there have been posts claiming that each is larger than the other. The room configurations are not identical but it would take an expert to describe the differences -- same for the resort themes!
BCV advantages:
Stormalong Bay -- best resort pool complex in WDW
somewhat closer to Epcot than BWV
close & convenient self-parking
BWV advantages
availability of standard view rooms for fewer points (if you can get one, which is unlikely)
significantly shorter walk to MGM
Boardwalk is at your doorstep
I sense that you are not a
DVC member. If not, I suggest that you not eliminate the Swan/Dolphin from consideration. If BWV and BCV don't work out because of availability or cost, 2 rooms at the Swan/Dolphin could work out well if you get a good discount. I believe each also has "junior suite" type rooms that sleep six. The pool complex at the Swan/Dolphin is underrated -- it is approximately the same size as Stormalong Bay. It is not as well themed but still lots of fun!