May I ask why Christmas is your favorite time, considering the crowds? I mean, it's crowded as all heck, yet lots of people love to go - why? What makes it worth it? (A sincerely, curious question)
Good question. For us it comes down to a number of things, no surprise there

.
Yes, it's crowded, but if you plan reasonably well and have realistic expectations, that's not a problem, at least for us. We're not all about the rides, we like them, but if we miss them one day it doesn't bother us, we'll get it the next day. We normally stay for about 3 weeks and on site, so have plenty of time to get around. The people add to the atmosphere, it's not like they are barging their way around (sure, some do but you get those people at any time), for the most part they are there enjoying themselves adding to the spirit. The decorations are lovely and even wandering through the resorts makes for a lovely few hours. The campgrounds are also fab, the way people decorate is incredible.
As to the crowds, we tend to avoid the parks at the really busy times. We hit them early, skip off during the day and come back at night when it's quite. A lot of times we will alternate really late nights and early mornings. EMH mornings are fab if you're on site. EMH evenings are not so great, IMHO, as the time taken for the lines to clear can sometimes be as long as the EMH itself. However we LOVE the really late MK opening. Then 12AM+ (sometimes to 3AM) is just so fantastic. On Dec 23rd last we did BTMR 3 times in a row, once without even getting out of the cars, they just sent us on our way again as no one was waiting. 7DMT was a walk on, Space as less than 10m. It was fab.
Of course you also have to be sensible. MK on Christmas Day or New Year's Eve, no thanks, we're not that brave.
We have kids in school, so school holidays are the only realistic time that we can go. Both DS & I would literally melt in the heat & humidity of the Florida summer, so it would not be the least bit enjoyable for us. We went around Easter in 2012 and that was lovely weather, but we still prefer Christmas. It can be cold the odd day, but cold for Florida is grand for us, it just means a hoodie, or sometimes a jacket, it's not COLD as such. We've used the waterparks and the pool at Christmas, no problem. In fact, it's a great time for the waterparks, there's only usually the more hardy northern US people (no offence to those in the south

) and the Europeans there, it's really quiet.
Christmas time is not for everybody, attitude (to crowds) and expectations play a vital part. If you are a family that likes marching from one ride to the next, maximizing the no of rides, then I'd definitely be saying don't go. If you have a more relaxed touring style, try it at least once. If you can make the time, try and either come early or stay later, at least you'll probably get one 'quieter' week.