Kind of depends on your taste!
If you like something on the fancy side, then go for broke at the Grand Floridian
If you want to be on the monorail line, but want a more laidback tropical feel, choose the Poly.
If you like the energy of a big city and the convenience of walking to the MK, choose the Contemporary.
If you are big into MGM and Epcot then go with the Yacht and Beach Club
If you like nightlife right outside your door, then go for the Boardwalk Inn.
If you want to be one with nature, and convenience is not an issue, go with the Animal Kingdom Lodge.
If you want a feeling of escaping from the hot Florida environment, and convenience is not an issue, go with the Wilderness Lodge.
Personally, I would be torn between GF, CR and Y&B Clubs. You could always split between 2 resorts during your stay, if you narrow it down to 2, and just really can't decide
Good luck