I say white. Sure, black is sexy, always has been, always will be. I chose white (male here) both because it will show less scratches and it is easily identifiable to being the largest iPhone model. Plus I do not have a case on mine (Carry it in a suede case when I'm not using it).
I have always thought of white products to be Apple. From the white iMacs and iBooks to the white keyboards to the original white iPods (white iPod earbuds are as recognizable as anything else out there in terms of who the company is). Most other tech gadgets, electronics, etc. are black, so it is also a way of standing out and being different!
Either one you choose will be great though so don't put to much into which color is right for you, especially if you're going to cover it by a case. You could be losing valuable time not getting able to play with your new iPhone everyday!