Pre ordered the black. Notice that the metal that goes around edges ( as on iPhone 4) is black as well. Assume this is not painted. If so concern would be scratches.
The reason that the metal is black is because it is made out of anodized aluminum. The white model is made out of regular aluminum. When you anodize aluminum, it becomes black and very dense. Also there are people who are sensitive and/or allergic to aluminum but if it's anodized, then it's not an issue. So I think the black model in this case is the way to go.
By the way, the iPhone 4 was not black on the sides. The sides were made out of stainless steel which is silvery in color. The same goes for the iPhone 4S.
