...travel by car or bus, CBR is right next door. I would have to agree that S/D are very close, as is BW as far as walking (or via the "friendships")!!
Boardwalk Villas are the closest to MGM, however since the Boardwalk Inn and Boardwalk Villas are rather spread out, I would say that the Swan, followed by the Dolphin is the closest hotel.
The Swan and the Dolphin are closest but we weere at the Boardwalk and the kids (24-28) including a 9 yr old - walked it - we (the grandparents) took the boat!
Either way It was great.
All those hotels have a great location to both MGM and Epcot.