According to famousmortimer PS4 has a 200k+ advantage on X1.
"So the November NPDs have come in and the results have some interesting implications and give a bit of a clearer picture of what each company’s current strategy is. Sony certainly coveted North America enough to secure the top spot but have resigned themselves to demand outstripping supply so they could take the rest of the world as well. Microsoft clearly has designs on not letting the United States slip away and have flooded retail since the launch. It wasn’t good enough to catch up in November, giving the PS4 a solid 200k+ lead going into December but with the Xbox One available nearly everywhere and the PS4 available almost nowhere it’s hard to believe that Sony will be the victor in December in North America. I think this should also put to rest the rumor that many people believed, myself included, that MS was having yield issues. Their console output has been extremely strong."
http://doddscientifics.com/2013/12/13/super-fun-sales-chat-2013/
