As I've said in another post, minor scratches that you're likely to get on the phone would be far less visible on a white phone compared to black (from my experience).Alas, this is my dilemma, too. A few dithery OCD points to consider:
1) I am a small bit concerned that the screen will look gray and less intense than a black one. To have a black front and a white back is really the ultimate route.
2) When you look at the screen on the Apple site it looks great, very bright and lively. But when you look at photos of it, it looks grayer and less attractive Of course, that might be the way that different media look on a computer, and real life is always different. And Apple is going to make it look as good as possible on their site, right.
3) And, if you own a white one and you don't have it next to a black one, the lack of comparison will always make yours look great.
4) There is always the old dull idea of getting a black one and putting it in a white case.