My buddy told me (after I posted of course) that when the cases started to hit Canada and reach the dealers, all of them had purple so as he put it "people in the know consider the black the variant."
Tough call, the case I saw had one of each, black and purple. Matters not really, it's a crappy figure. I will say the smaller head on the black looks better.
I think most people are looking at it with a McFarlane mentality - the picture of the regular figure shows black, not purple. But the picture also shows the variants of Bishop, Wolvie and Iron Fist. It shows nothing for X-23 at all. My guess is it's a running change.
Adding by edit: saw a bunch today at TRU, nada but black X-23 to be found.