X1 will win in the longer run, unfortunately for Nintendo there just isn't a large enough market for a "family" game console unless you have a fashionable/trendy new "hook" to sell it with (which the Wii U doesn't).
X1 will eventually drop to $349.99 and then $299.99 and none of its bigger games have really come out yet, whereas the Wii U has Mario 3D, NSMBU, Mario Kart, DKC, Nintendo Land, Zelda: WW, Wii Fit, etc. already spent.
At the end of the day it doesn't really matter who sells what for any given month. I think the upper end of the market that Nintendo has to sell to is basically about 20 million households. And that's assuming a fairly generous increase in sales from here on out, because right now it's trending to finish at around 15 million LTD when compared to the sales performance of previous Nintendo gens.
That's just not a lot. X1 probably isn't going to be as successful as the 360, but it should be able to top 20 mill without much fuss, even the original XBox sold more than that and probably would've hit 30 million LTD if MS didn't pull the plug on it.
