The sharper edges of the iPhone 5 series design does have its advantages. Grippier and easier to take photos. The 6/7 series design has got to be most slippery iPhones since the 2G. Rounded sides, flat back and matte finish doesn't help especially for the Plus models which is harder to grip in one hand.
My perfect size is about "4.5-"5 but just trim the bezels. Motorola since 2013 with the first Moto X and G probably is my most ideal dimensions and ergonomics. If Apple could increase the display about an half inch, give the sides a slight angle, curve the back, and lower the bezel with 130mm in height, that would close to the perfect iPhone size for me.
Some design aspects of the 5 & 6 design/ergonomics aspects and being the midpoint for each of their height would simply be perfect. Improve the Touch ID, display, and front camera too. But knowing Apple, they probably return similar to the 4 series if glass but edge-to-edge..
Whatever we see in some aspects from Android now (Xiaomi Mi Mix, Mi 5s), that's what Apple will go for but glass. You still want 3.5mm headphone phone jack and don't want camera hump? Do you want less smudges on the back? Then SE might be your only and final iPhone option with more than good enough specs.
Just live with the "4 display for a little more typing mistakes, fairly mediocre 1.2MP cam from 3+ years ago, and older Touch ID. But design-wise, gripping it with one hand, and snapping photos, it is close to perfect. The perfect iPod-like iPhone for running and working out.
I see the matte black iPhone 7 for the first time and just went "meh".. The so-called Batman iPhone looks like any other black phone that attracts smudges like crazy.
^ Most beautiful iPhones ever made.. Space gray 5s & SE. Slate 5 is also up there bur the Scuffgate. I like the lighter shades of gray from the SE because the lighter the color, the less smudges will show. And it matches a little more to the silver MacBooks.