Maybe this should be transferred to the Xperia S forum now?
In any case, unlike most here I prefer the white one from the front as I like the contrast. But, I'm afraid there's too much white for my taste on the back.
As far as the black one goes, I don't think the bottom plastic part will blend nicely with the deep glossy black bezel surrounding the screen, as the plastic will just look a little "less black" and not very integrated if you know what I mean.