Stormalong Bay is the best overall pool, but there are several in the next tier down which are all very close.
The Polynesian, Grand Floridian, Coronado, WL, and Dixie Landings are all a very close 2nd.
Stormalong Bay (YC & BC) is centrally located, and within walking distance of Epcot, a short boat ride to MGM, and a bus ride to AK and MK. It's also close to the Boardwalk, which can be a lot of fun.