Its definately a toss-up between the MK Resort Area and Epcot, and I can give my reasons for both...
I really love the MK area because resort hopping is one of my favorite things to do while in wdw. It is easier to resort hop from the GF, Poly, and Contemporary and much more fun using the monorail and the Poly is my favorite resort to have a meal and just take in the atmosphere.
The Epcot resort area is great because I can take the boat from DHS since I never spend a full day there anyway. Get off at any one of the resorts and make my last stop to the Boardwalk and walk around and go to my favorite...ESPN!! After exploring the Epcot resorts, nothing is better than walking over to Epcot from Boardwalk and walking around WS!