I dislike them all I think:
The 'vintage' or 'classic' ones are so over-played they now completley grind and simply conjure up the imagry of shops playing it 24/7 to get people into the 'Christmas Spirit' and hence spend more in the shop.
The modern tracks usually are ripped off from older ones or a normal songs but with silly bells added into the tune. These seem to be yet another way of getting money out of people by getting the christmas number one in charts.
However, there is one beautiful track which is sometimes played in church christmas ceremonies (been a while since I've been to one to be honest) which is kind of christmasy. It's called Lully, Lullay I think and it's pretty damned sweet. I believe Charlotte Church has covered it, but I've not heard it, I've only heard versions sung by church choirs....