The nice thing about staying at Beach, Yacht, or Boardwalk is that you can enjoy all three just walking around the resort bay and see all their Christmas decorations. Boardwalk's isn't quite at the level of Beach and Yacht, but still very nice vintage style decorations.
A few shots of Boardwalk done up for Christmas:
If you want to try different areas, Grand Floridian is highly visited for its Christmas display with a massive tree and a huge gingerbread house that serves snacks and beverages.
As already mentioned, Wilderness Lodge is beautiful at Christmas and with the northern park lodge design feels the most seasonally 'Christmas-like'.
I'm at Disney World every December, and no matter where I stay, I usually take time during my trip to tour various resorts to enjoy their Christmas displays. Other resorts I like to visit are Animal Kingdom Lodge, Coronado Springs, and Fort Wilderness Campground (some of the Christmas displays that the RVers and custom busses put up are stunning).