At MK, Uber/Lyft will likely save some time because they can use the new flyover to bypass the parking toll booths, but during Christmas week in the morning there will still be some delays, as traffic into MK can back up all the way to Epcot or beyond. At the other parks, there aren't really any shortcuts, and Uber/Lyft have to wait in line to go thru the toll booths like everyone else. You will save the time of waiting for the parking trams and will be dropped off fairly close to the park entrances. DHS is a mystery, because there's no knowing what the parking lot and drop-offs will look like by December.
Be aware that Uber & Lyft adjust their fares depending on demand, so the amount you'd pay, especially at park closing on a full capacity day, might be significantly higher than what you might see now on the apps.