It’s actually more than a little tough after you discount AK.
Of course the big thing at DHS is the Osbourne lights and their tree is outside the park (as is AK’s). I don’t think they really have much else and if they do, I’ve never really noticed more than light pole decorations.
So that brings us to Epcot or MK. Unless you do the Christmas party in MK, it’s mostly window and light pole decoration with the tree in the flagpole square. If you do the party, you get a special parade and fireworks show as well as all the holiday costumed characters. Down side, this is a hard ticket event and the absolute earliest you can enter MK with that ticket is 4 PM with the park closing for non party guests at 6:30.
On the other hand, Epcot has a special version of Illuminations every night at 9:30, three performances of the candlelight processional, and “Christmas Around The World” with each of the countries featuring their own versions of Santa Clause (Father Noel in France, etc.). This is all part of the standard admission and you can enter the park at rope drop and stay until it closes after Illuminations.
You have to decide which of the two parks to do.
I’m assuming you’re only planning to be in Orlando for one day.
By the way, they have Santa Goofy in DHS by Streets of America during the Osbourne Lights.