If not staying on property during Chritmas, your wait times will be anywhere from 45-120 minutes, depending on the ride. If you are't staying onsite, your best bet is to get to the park very early in the am & do as much as possible. By mid morning/early noon...it will be mobbed. There were times, with the FOLT room key, I saw 30 minute waits....
Presidents weekend will not be as bad as Christmas. Those waits may be from 30-90 minutes. If staying onsite, there should be really not much of a wait, maybe 15 minutes or so. If you have a choice, I would say Pres weekend since the lines are shorter, but then again, Christmas time is really nice there. The Studio's has the Macy's T-Day parade & IOA has the Grinch & all the Who's from Whoville put on a show. You will not get to see that any other time.