You have your smartphone 5" from your face? Why?
I do that, too--well maybe not quite that close. More like 10 inches, and am also pretty sensitive to ppi. I definitely notice the "dottiness" on the smaller IPhone and on the larger iPads. I stick the iPhone close up to my face because I'm nearsighted without my glasses. But I'm middle aged, so with my glasses on, I can't see the screen clearly, either.

So I'm stuck taking off my glasses and sticking the screen up close to my face.
I do think the iPhone 6S plus has a nice display but I do tend to stick that up close to my face, too.
I can read the Note 7 screen easily from a normal distance with my glasses on. I don't really know how to account for the difference. But even on the Note 7, when playing a hidden objects game I will take my glasses off and stick the phone up close to my face.
I think the SE ppi is well matched for the size of the display. I think the iPhone 6 display could use a boost.
I noticed a loss of detail on the iphone 6/6s vs IPhone 6Plus/6s Plus when comparing photos from Google earth at the Apple Store when I was trying to decide between the two sizes.
I do think there are genetic things at play with vision. My dad before age 45 and I also before age 45 both easily used to be able to do really fine repair work on tiny things with our naked eyes that most people could not stand to look at without a magnifying glass. But we are both really nearsighted. And now in later years are farsighted as well.