Am wondering whether the 4/s has more internal real estate, or the thickness is just due to the back glass?
Apple used a smaller battery in the iPhone 5 presumably because they made it thinner. So the battery and the CPU/OS is more efficient in the iPhone 5 considering it gets better battery life. They could of made it as thick as the 4 and got much longer battery life. However, I don't see them going back to a thicker phone. That would make no sense and the press would kill them over it.