I think this is a very cool concept for a photo shoot. The fact that one outfit is essentially a photo-negative of the other is very intriguing and the fact that it's carried to the hair only adds to the intrigue.
While clearly not an option given the photo shoot models, I do think the idea could have been carried just a bit further with the use of a darker skinned model in the white dress to make the contrast all that much more distinct. That said, it definitely doesn't detract from the photo.
The expressions are also somewhat contrasting in that the one on the left seems to me to be a "yeah, this is what I wore, what are you going to make of it?" type look while the one on the right has more of an inquisitive look, almost as if she's giving the viewer the same once-over that we're giving them.
Lastly the background color helps pull it all together by matching up well with the lipstick and then ranging from the almost black shadowed portion at the bottom of the photo to an almost white look in the middle as it's lit up by the flash, only to transition back to a darker color on top.
All told it adds up to one spectacular photo and leaves me wanting to see more.