> As the size of our hands hasn't changed, how can a 4.7 inch phone now be perfect when previously 3.5 inch was deemed perfect? Here is one reason: as the devices become slimmer, your thumb can reach farther than before and hence cover a larger screen.

Well, I'd say most of the problem here is trying to identify a two-dimensional screen by a single number, the length of its diagonal. It must make more sense to give the actual dimensions of screens.

I remember pained discussion of the Nexus 5 saying the 4 was wide enough. The 5 is only wider by a couple millimeters, but is significantly enough taller that they bumped the single number identifying its size. That's no way to communicate.