It might be the paint or an extra layer of protection that made the recently released, after almost a year of delay, white iPhone is 0.2mm thicker than its black version. In the white iPhone, the metal antenna band is just the same. The only difference is the thickness of the glass panel. It is a bit thicker.
Announced on June of 2010, the device was delayed for more than 10 months before being released. Apple’s Phil Schiller told that extra UV protection had to be added for the device to work properly. The exact reason is still unknown, some think the problem was with the plastic that discolored over time.