Going from the 6 Plus to a 7, I noticed the drop in PPI and resolution. The screen always looked blurrier to me. I may be more sensitive than some, as I used to do video QC work. The bigger the screen gets, the more obvious a lower PPI becomes for me, considering I hold my phone closer to my face than I hold my iPad (the further the viewing distance, the less obvious the lower PPI becomes).
If the screen were at least 1080p as it is on the Plus phones, I would have gone with an Xr. I would miss the telephoto lens, as I appreciate the optical zoom, but that would be a small sacrifice for the improved battery life and lower price. However I know I couldn’t live with the lower PPI screen especially as the screen itself gets bigger. Just my line of thinking.