Some Cases Don’t Fit the White iPhone 4
It seems that a white glass color and an improved proximity sensor were not the only changes that Apple made to the white iPhone 4. It is actually ever-so-slightly thicker than the black variant. That’s because of a taller piece of rubberized plastic running around the front and back of the phone.
As you can see in the image, the extra height that the taller rubber adds makes the white iPhone 4 noticeably protrude above the older black version. Since the rubber goes around the shape of the glass, it keeps the glass in place while also adding a bit of general and shock protection. TiPb measured the rubber to be .1mm thicker on both sides, making the white iPhone 4 .2mm thicker overall.
Some tight-fitting cases, such as the Incase Slider, have been found not to adhere to the white iPhone 4 well, if at all. Many of the cases that TiPb tested fit without any major issues, but slider cases could present a problem.
While I would assume that the increased rubber thickness does undoubtedly add at least a little extra protection from scratches (due to its protruding above the glass) and drops, it is a little odd for Apple to make the minor revision to a variant of its iPhone 4 since it breaks the white iPhone 4′s compatibility with a number of cases. There is a small amount of irony, but better “bare protection” isn’t a bad trade-off.