Boardwalk:
You can walk to Epcot
It's a slightly long (but manageable) walk to DHS
Very nice CMs
Ok pool area
Nice evening entertainment
Rooms in desperate need of refurbishment (a.k.a. SKANKY)
Larger rooms
Cheaper to buy
Higher annual dues
Beach Club (Disclaimer, I have not stayed yet):
Nicest and biggest pool on Disney property (one of the few that doesn't allow pool hopping visits)
Newer rooms
Close to Epcot
Walkable (though far) to DHS
Smaller rooms
Fewer dining options
Higher buy in cost (at least in resale)
Lower annual dues
Regarding the bolded items above:
I know that Disney has different published room sizes for the two resorts but they are essentially the same. Their numbers for the sq footage has changed over the years and I don't know where they came up with the higher numbers for BWV. The layout is almost identical and even if there are differences, you couldn't tell after walking into the two.
As for the condition of rooms and quality of CMs, I just want to say that those aren't great criteria for making a buy/don't buy decision. CMs come and CMs go. Some rooms are well-maintained, others are not.
We had a room at the BW in '08 that was in excellent condition. We could smell the cleaning solution when we walked into the room (a GOOD thing, IMO) and there were no noteworthy issues with paint, carpet, appliances, plumbing, etc. BCV is the newer of the two (by about 6 years), but they are both high traffic resorts. The differences between a 13-year old resort and a 7-year old resort are negligible. Most times it comes down to how recently the room YOU are given has been refreshed.
In addition to what others have said, here are a few other comments about the two:
BWV
* Inconvenient self-parking
* One set of elevators (a lot of people talk about the "long hallways", but in reality it's about the same distance from the BC lobby to its villas. The bigger issue for some is the fact that the only elevators are right off of the lobby. If you can use the stairwells, the resort size isn't a big deal. But if you have to walk to the elevators each time it can add to your journey.)
* No counter service dining
* No restaurants actually in the resort (have to go outside to reach a restaurant)
* Excellent room views (canal, pool, BoardWalk)
BCV
* Very convenient self-parking
* Two sets of elevators--one right in the Villa wing
* Long walk to Stormalong Bay pool
* Very poor transportation to DHS (walk is a good 25+ minutes, only other alternative is boat)
* Have to walk outside while going from lobby to Villa
* Villa room views are mediocre at best; about 1/4 of the villa wing sits alongside a busy roadway