Well, I hear that time of the month is nice and quiet anyway. The earlier week is the week of the DVC board meetings, so alot of extra dvc'ers will be running around, so I'd guess the later weeks will be quieter.
This is actually for 2004 , but based on this year, the airfares seem higher that first week and 1/2 - the rates seem to drop later in the month (before Christmas week anyway).
This year there's some big conventions going on that first weekend, and WDW rooms are sold out at a lot of places. I don't know if it will be the same next year. I'd go with the second week just to be on the safe side. Plus since it's closer to Christmas, it will feel even more festive.