Xmastime is a magical time at Disney. If you've never been during this time, you should go. The resorts are decorated with beautiful trees and lights, and the Osborne lights are spectacular! However, if you're going more for the rides or if you've seen the parks at xmastime, your best bet is to go before the schools let out. Another thing to consider is the room rates if you want to stay onsite. Value season will be through Dec. 19, whereas May will be in Regular season. There may be a significant difference between the rates depending on where you stay. For me, personally, I like the xmas atmosphere and the spirit that is in the air during this time. Hope this helps!