Well, I'd take black. Because the 360 is black, the Ps3 is black, and the Wii Remote and Nunchuk are also black. So why not get a black console? If it comes out on release (unlike the Wii) I'll grab it. Otherwise I'll settle for white since darn I want those games pretty badly.
I've always liked the white color, it's part of what made the Wii unique when it first came out. I have a white DSi, too. It just looks... clean, I dunno. Doesn't smudge as much either.
Hmm, this may be a challenge. My favorite color is black, but the white Wii U looks nice just as the black one does. I think I will just get the black one.