I prefer instrumental and orchestral renditions of traditional Christmas songs over croony Bing Crosby-ish ones. I also have a fondness for Celtic twists on Christmas tunes. I think my favorite song out of all of them is Carol of the Bells (this particular one has both a full orchestra and a Celtic twist). I like the build in the song to a powerful climax, which is stimulating and moving, and I guess I find the song to be beautiful in general.
Another one that is a definite favorite is not a traditional Christmas song. It came on a Windham Hill Celtic Christmas CD I bought fifteen years ago and practically wore out because I loved it so much. Loreena Mckennitt – Snow (hopefully, the link works)
My mom is absolutely nutso over Christmas music and plays it (and no other kind of music) from the day after Thanksgiving until Christmas. It honestly gets pretty old. Between her, other people, radio stations, and store music, by the time Christmas actually rolls around, I’ve heard Christmas music constantly for a month, so if I have any control over the matter, the only time I play it is Dec. 24 and 25. :)