I toured most of them last Dec. My vote for Fav was Beach Club. Each person definitely comes out with a fav & you will too. Ya' just have to wait to see. I couldn't fit it all into one evening (w/a nice meal break in there along the tour) & had to finish up another day.
I think that the Beach Club has a =n amazing Holiday display in the lobby, and always budget time n to explore it along with the rest of the Epcot resorts. Usually before dinner.
I also take the time to check out the monorail resort lobbies, with the Grand being my favorite. I generally break up the tour into two days so that I can add it in when I am heading for dinner at one of te monorail resorts or at Wilderness Lodge, which has a stunning tree in the lobby. I tend to start at or finish at WL, and take a boat to or from CR.
We usually arrive on 30th December and don't have park tickets until the 1st January so spend New Year's Eve going round the resorts. Absolutely love it but have to say it takes us the full day (and we're up at silly o'clock because of the time difference) and we don't get everything done. Last year we got a bus to MK then did the monorail resorts starting at Poly and finishing at Contemporary. We then got the boat to Wilderness Lodge (disappointed the tree had already gone) and then a bus to DHS. Boat to Boardwalk then walked round Yacht Club and Beach Club. We were done for by then so headed back to AoA and caught up with the others later on. Staying at CBR this year so will more than likely start with Skyliner. Have fun.
I love GF decorations but am not crazy about the Poly or CR, WL is beautiful though with decorations all over the place.
For bang for you buck, I like the Epcot resorts for seeing decorations. Big ole choc. carousel at YC, cool as heck little village with a train going around it at BC, pretty trees at BW, big ole choc. santa workshop at Dolphin.
Then there is AKL, which has one of the biggest trees I've ever seen. Don't discount the moderates either, some of them have some great decorations.
So, I guess you can't go wrong with any resort(s) you decide to visit.
We tend to take an afternoon and do the monorail and WL resorts on a day we are at MK. Then take another afternoon and do the Epcot resorts while walking between HS and Epcot. Then a hour here or there and bus hop to some of the moderates or AKL when we are leaving AK.
When we go at Christmas it is with the understanding that the parks are going to be crowded as all get out so our focus is more on enjoying the look and feel of WDW and less about riding rides.
I agree with several of the others who have posted. WL is my favorite followed by GF. I also really like the BC and YC decorations, just not as much as I love the first two.