I think you're spot on. The more I've paid attention, the more I've realized I use my 5 with one hand, more often that I had thought. However, when my 6+ arrives, I'm sure I'll just get used to using it 2-handed. Just as we will reach for the power button at the top and eventually get used to reaching for it at the top right of the 6.
Am I the only one who takes calls on my phone with headphones 99.9% of the time? I almost never put a smartphone to my ear.
I use my iPhone so little as a phone that most of the time it is used in speakerphone. Mostly in the car while driving or at home while cooking dinner and the wife calls on her way home with one of the kids.
I'm telling you, I use my phone as a phone for probably 40 mins/month. All the mins on my monthly bill are from my wife since she actually talks on it. Now if I was going to upgrade my wife from her iP5, it would definitely be to the 4.7" model The + model would be too big for her.
So there are benefits to both models and I not bashing either of them. So far, my 6+ is a big change for me but then again, I wanted something betwen my iP5 and rMini. I think this will do it. Looking at getting a BT headset for those infrequent calls so I don't have to hold the phone to my head. Otherwise, I will stick with speakerphone.