Christmas crowds are larger
The simplest objective evidence of that is that it is common for the MK to close due to reaching capacity for a few hours on several days around Christmas and that is rare at Easter. It makes sense because school breaks are not all at the same time during spring break and Easter, whereas everyone has the week between Christmas and Easter off.
That having been said, our approach to touring is the same at both times and the results are largely the same. The biggest key for us is taking advantage of expanded park hours, especially early EMH. Usually the MK has EMH at 7 AM during that week, and if you can get to those you can enjoy a lot of attractions before 10 or 11 AM. Then you can slow down and do some of the "anytime attractions", or take a break away from the parks when the crowds are at their peak.
One of our favorite afternoon activities at Christmas is visiting the resorts, as several of them have excellent Christmas decorations and displays.
It is definitely worth doing at least once. If you have experience dealing with Easter crowds you'll have a great time.