I have a medium guys hand and I can barely reach the top of the 5 with one handed use and have dropped it a few times when doing so. I made a cardboard approximation for the 6 based on its specs and I can only reach the bottom 3/4 of the screen, no way I can reach the top with one hand. For that reason I'm going for the 6 Plus for its added benefits (it's massive but still fits in my jeans pocket).
Maybe it's the way I hold it. I'm one of the "you're holding it wrong" guys. My hands fit in medium gloves perfectly.
I do that too and it's just too easy to drop that way since you don't really have a good grip. I've got two small kids. It's an issue for me.I hold my phone with my pinky underneath. I push towards me with my index, middle, and ring fingers to bring the top of the phone toward my thumb when I need to reach the top of the screen.