DL is magical at Christmas time and my family and I love just walking around and taking in all the decorations and atmosphere, but prepare yourself for pretty big crowds during the week leading up to Christmas. All schools will be on vacation and it is a popular time of year. Early morning may be OK, but crowds will likely build fast. We went on Christmas eve a few years back because we thought the crowds would be lighter, but we were quite wrong.

The week between Christmas and New Year's is
much worse though, so if you had to choose one or the other, I'd definitely go with the the earlier week.