This is kind of how it breaks down:
If lighter crowds are the most important thing (and also shorter hours, along with a more limited entertainment schedule), then the absolute best time to go would be in between when Halloween Time ends (after 10/31) and when the holiday season begins (which is 11/12/12 this year), and even before Veterans Day weekend. That 'between season' time frame is lower in crowds, for obvious reasons.
If you want to have the holiday experience - and I am using the word "experience" because the holiday season at DLR entails more than just decorations - and you want to know when the best time to go (with the lowest crowds) is during the holiday season, then it would be (as others have said) the week immediately after Thanksgiving (in other words, starting Monday after the holiday weekend) or the first week in December.
This post-Thanksgiving/early December time frame will probably not be as light, crowd-wise, as that first week or two in November (before Veterans Day weekend), but it will be the lowest crowd point of the holiday season, while still offering the full array of holiday entertainment, food, ride overlays, decorations, Santa, carolers, snow on Main Street, etc., etc.