It isn't the size that counts - it's the SIZE that counts!

I'm reposting my comment as Good OL MC from a Rene Ritchie iMore article:

http://www.imore.com/why-5-inch-iphone-far-more-important-13-inch-ipad

An iPad with an even larger screen doesn't add much to the table. Tablets can get pretty awkward once they are bigger than the current Air - and I lump the previous iPads in with that statement.

If anything was proven to me in 2013 it was that a phone with a big screen can be incredibly usable with one hand with no juggling. The phone that proved it was the Moto X. Despite the flaws it has I find it hard to argue with the ergonomics of the device. And, like you said, software can fix any other one handed troubles. I'll just add to that by saying software does that so long as the phone is still easy to hold. If Apple can negotiate that compromise it will be a success.

It isn't the size of the screen that matters - it is the size of the phone.