I've done the Halloween and Christmas parties. I liked the Christmas party far better.
1) I thought the parade was better. In fact, I thought the
MVMCP parade was the best parade I've ever seen -- hands down. Very kid-friendly, too.
2) I loved the snow on Main St.
3) I found the crowds to be far, far smaller. (We went to a very early Christmas party, as opposed to a Halloween party close to Oct. 31st -- so that probably accounts for the differences in crowds.)
4) I liked the hot cocoa and cookies better than the Halloween candy.
I really expected to like the Halloween party better, and was surprised when I liked the Christmas party far better.
My DD was 5 years old when we went and we closed the place down -- the last thing we did was the Candy Cane character meet and greet near the front of the park -- and had a great moment w/Winnie and Eeyore. And it was a walk-up to meet them -- no lines.