Welcome to the Dis!
I dont know about the best, but supposedly MK is the worst. We will be spending our first Christmas in WDW too and we plan to go to MK for EE, just to 'be there" for Christmas. Then we will have a late breakfast at either Cindys or Chef Mickeys(whichever we can get). Since crowds are supposd to be really bad we plan to take the rest of the day to resort hop and check out the decorations all around WDW.
Good luck deciding.