My trip last year began on Sunday, December 4 - the second day of the Candlelight Processional. Even though it was a Candlelight Processional day, the crowds were not bad early on. They only picked up in
Disneyland around mid-to-late afternoon. However, a Facebook friend told me the crowds were awful the day before (Saturday).
We assume the CP will take place on December 1 & 2 this year (not confirmed yet). But you can plan it so that you're in California Adventure when the Processional starts in DL, in case you don't want to risk running into crowds. After the CP, the crowds cleared out and it was delightful around DLR.
Personally, I really think that the overall experience one gets when they go during the full-throttle holiday season (meaning everything is up and running) is worth
some crowds (within reason, of course) in comparison to going when there are just a few things up here and there and none of the holiday entertainment has kicked in yet, but the crowds are lower. In other words, if someone is a Christmas fan, I think that waiting to go when the season is officially underway is well worth it, even if it will be more crowded than the first few days of November.
But it really all boils down to you and how much you want that overall Disneyland Resort Christmasy experience again
or how much want lower crowds this time around.