Just for fun, I checked today's USPS
ebay listings for Holiday Stamps sold, which resulted in this interesting graph of what are the "best sellers":

Of course, it's only based on
ebay sales as of today (12/12/2013), since the USPS Store's website doesn't provide such sales info., nor does it include retail sales at post offices. No matter, it does give some insight into the popularity of stamps for this Holiday Season.
No surprise that the Gingerbread House stamps take the lead, however, since both the 2012 and 2013 Holy Family stamps are essentially the same except for the format and date, if you combine those sales, they actually exceed the Poinsettia in overall sales.