When it comes right down to it, what I like about the Christmas music is the plethora of interpretation. You take a body of work, and let a whole mess of people at it, and you get a whole mess of variety. Seventeen recordings of Beethoven's Op. 111 are all going to fall within a narrow range - all the notes will be there, and while there's a little room for interpretation in tempo and dynamics, it's going to be pretty straight ahead. (But Maurizio Pollini's is the best.) Seventeen recordings of Silent Night are going to be all over the map. Vocals, no vocals. Brass band, full church choir, musical saw. Straight 3/4 time, swinging 5/4 time.
The covers by jazz performers are some of the best. Take something you know, and pull it apart into seventeen explorations. Or maybe, create something new using lots of familiar elements. Like yesterday's River, today's Bobby Watson track, Vauncing Chimes, starts with a riff on Jingle Bells, goes off on an ecstatic jazz explication, weaves in some Hark the Herald Angels Sing, and blows the roof off the house.
Besides, who can resist something called Vauncing* Chimes?
* Yeah, look it up. It's an obsolete word meaning to advance.