I'd have to disagree on the S versions being small bumps. I think we see bigger bumps with the S versions. 3GS from 3G was noticeable improvement. 4 from 3GS performance was little improvement except for the retina display. 4S from 4 was by far the largest difference of them all. 5 from 4S was meh.
Biggest from 4S to 5 was the screen which was more importatant to me, Camera, Battery, Screen are the things I look for and I agree the 4s was great but the 5 had a .5 bigger screen made a big diff for me