We only own at BCV, but previously we owned at OKW. For US, the different room setups are also a factor. It is easy to look at the diagrams and think there is no difference. We have 4 kids, and always book a 2BR. At BCV, we can get the dedicated 2nd BR with 2 queens (or full?) beds. Huge advantage for us, we prefer it, as pulling out and sleeping on the couch every night of every trip is a pain. 2nd, in the master bedroom, we like the toilet being isolated behind it's own door. Again, we are a big family, and that makes it easier for us..... My teens love the daily pool volleyball in the SAB pool. The VIEWS are so-so as others have stated. Quick walk to Epcot. VERY easy to park at BCV, you can always park pretty close and go in the side of the building. We have an alligator, too.
That said, I also love Boardwalk. I stayed once in a BW view room with a friend, and I will truly never forget it. Fantastic. I love the slide at BW myself, more so than the one at SAB. If your family is not large like mine, you may prefer that couch in the 2nd BR, much more comfortable to watch TV, etc on a couch. BW has grand villas, at BCV we do not.
You can't loose with your choice.