I have awful eyes and giant glasses: I just tried all three side by side, F3hp is the best, it's uncluttered and the info at the top is super easy to read (except in the dark, but that's a different problem), F5 is second, both top and bottom displays are totally readable, bonus points for lighting the bottom display, penalty for not being able to tell which AF point is active in poor light, F4 is the worst, both top and bottom data and corners seem slightly out of view, plus if you look through it a long time, there is an annoying (IMO) central hotspot.
That being said, I wouldn't rate the viewfinder as all that important; I used a Pentax 67 for a long time, and I could only see the very central part of the screen.