We have stayed early December many times, usually during "jersey" week. We have stayed anywhere from Dec 3rd to 17th, and loved the decorations and lower crowds. However, we have not been back in December for at least 4 or 5 years, so there might be changes I am not aware of. I will say it was always a great time to go.
Then we switched to early Nov at least a week before Thanksgiving. We had lower crowds and it was great. You can get Halloween dec's and Christmas dec's if you time it right

That was our absolute favorite time of year to visit. However, last year we had to cancel our November trip due to health reasons, and rescheduled last February. We went in Feb, 2017 from the 7th to the 17th and LOVED it. The weather was great, 70's at day. We know we were extremely lucky to get such good weather. The BTG's were almost nonexistent during our trip. We saw only 2 small ones and had no trouble at all. There were a lot of cheerleaders, but no problems there. We just did not get in line behind them.
This year we are going end of Feb/first of March. I hope we get the same great weather. I kind of like the non-decorated parks since I have visited during all the holidays before. It was kind of nice to see Disney in it's natural state LOL.
I would still rank November as #1 and February as #2 on our list of favorite times of the year.
Hope this helps.