I've had every iteration of iPhone since day one. Palm Treo was my device before the first iPhone. Actually not a bad piece of crap.
Having said that, since day one I have upgraded to every iPhone except the "c" and "se". This includes trying both screen sizes of the 6 and 6s series.
Periodically in that time I have also dropped iPhone just for shitz'and'giggles a few times trying the BB Storm 1&2, Samsung S4, Samsung S7 Edge, and an HTC Somethingsomething.
Having done all that, screen size and screen quality was actually the main factor in most of those choices. As users, our first and only real connection to these devices is visual, if not intellectual.