Yeah I just figured that it wasn't to scale... Looking on http://phone-size.com it seems like it is to scale. So that diagram is clearly biased and hurts his argument, but I think that what he says is still valid.

I don't see any advantage to having a bigger screen. Especially when the bigger screen has less pixels (i.e. Galaxy S II). In that case, you actually have less pixel space for UI elements, text, video, etc. than you would with the smaller, denser screen.