Hi Robyn! This is a question many guests ask during the holidays and it is a tough decision for many reasons.
If you are thinking about crowds and want to head to the least crowded park it is likely going to be
Epcot on Christmas Day. The
Magic Kingdom is the most popular with families to enjoy the special holiday at and being much smaller in size then Epcot you will feel the crowds more in this park.
Epcot is going to be busier then usual though with the opening of the new
Frozen Every After attraction. Lines have been long during this first opening week and it is likely to be one where lines will form early when the park opens. Another new attraction has had a major refurbishment and has brought new filming and that is
Soarin. It has increased its capacity so the lines are long but much better then before.
My vote will still be to head to Epcot as finding dining there will be much easier too on a holiday. There are wonderful choices in the World Showcase with a multitude of
Restaurants where you can make reservations. Consider making a dining package for the Candlelight Procession and follow that with the holiday Illuminations show.
My last reason my vote goes to Epcot is because
Mr. And Mrs. Claus can be found in the American Adventure Pavilion. I have always found these lines are shorter then the lines in the Magic Kingdom.