If you mean in 2020, you should not expect that Nov time, which includes five days, Sat to Wed, of Thanksgiving week, to have smaller park crowds than that Dec time, Both will be crowded and that Thanksgiving week time may even be worse.
My personal choice would be Nov time if it were not mostly in Thanksgiving week. You get all the Christmas decorations and have a much lower risk of getting any cold weather. Nov is usably very pleasant weather while that time in Dec, though often nice, can sometimes have a cold front drop down from the northwest direction and send daily high temperatures to low 50s with even possibly 30's at night.