I've debated this too much.
They both look gorgeous. The black is a neat slate, but it is prone to chipping the finish off especially on the edges. At first I hadn't seen any phones that didn't have some scuffing, but I've since seen some that look perfect, so it is possible. The perfect ones were demo phones at an Apple store with VERY heavy use, so it must be pretty rugged.
The white is awesome. To me it doesn't look cheap at all. The worst thing about it is that it looks like the white iPhone 4/4s. The edge glistens in the light making it seem almost jewel like. The back is mostly aluminum, like the Macbooks. Overall, I don't think the phone seems girly at all. Its really good looking. I generally think the white looks more cheerful. I've had black Android phones for years and wanted a change.