iPhone 3GS: How thick it feels (top) versus how thick it really is (bottom). In the top photo, the 3GS doesn’t look as thick, at least not much more than the 4. However in the bottom photo, the difference is much more readily apparent. If the iPhone 3GS wasn’t rounded (imagine it being box-shaped in the bottom photo) it would have felt thick. Rounded designs, of course, are less space-efficient.
Another thing about impressions: The edge around the iPhone 4′s glass is plastic, but unless you notice this, it does look as if the glass is very thick, which it isn’t. This edge is probably necessary to stop light shining in from the sides. The metal antenna band, being about 2/3rds the thickness of the phone, but very prominent in contrast to the black edge around the glass, gives the phone a visually thinner impression in a different way to the 3GS.
