Earlier quoted context omitted.
I used to be in your camp but honestly, after using iPhone 6 (not PLUS) I am okay. I actually don't use my phone all the time. It is mainly sitting on my desk or in my pocket on the go. My hand is not huge per se, just regular size, like any grown up male in his 20s. Comparing to the old model with smaller screen, the larger screen does increase read space which is quite pleasant. Give it a try.
If you really want to use an iPhone 6 or 6 Plus with one hand, just double-tap ( not press, tap) the home button and the software adjusts the display size for you.
Unfortunately, I found even the 4" too large for completely comfortable one-handed operation. Shame I'll never see another 3.5" iPhone option.