Well... now that iPad, iPhone, is ...'commoditized' lack of better word (or nonword), its wise for Apple to look to expand the line up. Single focus is good for new category etc., but now that they set the bench mark... take advantage..
I have these use cases regarding display etc... just my opinion of course.
1) everyday walking/sport device/phone... 3.5 is perfect. Dont need or want anything bigger.
2) Driving... needed a bigger screen for maps. (Id consider buying a...