Well, we usually spend Thanksgiving with my family because my parents and DH's live about 6 hours apart, so there is no sharing. My MIL usually has to work the Friday after Thanksgiving and typically they would spend it with DH's aunt and uncle. We went there before we had kids and drove the 4 hours each way all in the day. Now with kids, that is just too much driving.
As for Christmas....it is my FAVORITE holiday. We decorate the weekend after Thanksgiving. Since we had the kids, we decided that we wanted them to have the majic of waking up in thier house and Santa having been there. And not to mention that our two are the only two Grandkids on both sides, so instead of having to choose between parents, we host everyone here. It is only our immediate family that comes and I love having everyone here.
We usually have another Christmas with each parent at their house on a different weekend. I also have a baking day with my mom and sister where we crank out cookies! Yummy and fun!