I was at the parks on Friday of that weekend this past year and crowds were very heavy! I would say that since that's probably the start of Grinchmas, IOA would draw more crowds. Both parks should be pretty crowded, however.
I was at US for Thanksgiving 2000 with my DH and two DS. The crowds were very heavy then much to my surprise. I thought it would be the perfect time since everyone (or so I thought) was at home having turkey. The parks were loaded with folks from Europe and other parts of the world. Then light dawned on Marblehead. It's only a holiday in America! Duh...