How will the size of the fonts typically compare on the XR to the 7+ or 8+? If the fonts are smaller for some reason, along with the lower ppi, that may make the Plus models more desirable to me. I want to move from my 6s to a larger screen because of my vision, and reading news or forums play into my choice. 326 is okay for me if the fonts are a little larger than on the 4.7" models. This thread has be opening my mind to the possibility of an 8 Plus, though I really want to check out the XR first.
Let's go through the numbers:
iPhone SE: 1.96" wide with 320 screen points = 163 points per inch (which is half of 326 ppi)
iPhone 6s: 2.3" wide with 375 screen points = 163 points per inch (which is half of 326 ppi)
iPhone 8+: 2.7" wide with 414 screen points = 153 points per inch
iPhone XR: 2.54" wide with 414 screen points = 163 points per inch (which is half of 326 ppi)
iPhone XS: 2.45" wide with 375 screen points = 153 points per inch (which is one-third of 458 ppi)
iPhone Max: 2.71" wide with 414 screen points = 153 points per inch (which is one-third of 458 ppi)
The lower the points per inch, the larger the font size.
However, all of the above phones except the SE and XS can use Zoomed Display mode. If you use this:
iPhone SE: (Zoomed Display mode not supported)
iPhone 6s: 2.3" wide with 320 screen points = 139 points per inch <-- This turns it into a giant iPhone SE.
iPhone 8+: 2.7" wide with 375 screen points = 139 points per inch <-- This turns it into a giant iPhone 8.
iPhone XR: 2.54" wide with 375 screen points = 148 points per inch <-- This is the odd one out.
iPhone XS: (Zoomed Display mode not supported)
iPhone Max: 2.71" wide with 375 screen points = 139 points per inch <-- This turns it into a giant iPhone XS.
So, for people with bad eyesight, the best setup to use is Zoomed Display mode on the Plus or Max. The XR is an interesting compromise though, since it can use Zoomed Display mode, but with smaller fonts. However, XR in Zoomed Display mode still has bigger fonts than all other iPhones in Standard Display mode including the XS, while displaying the same amount of information as the XS.
IOW, XR with Zoomed Display mode turns it into a big XS, but not a giant XS. To get the giant XS as indicated above, you need a Max with Zoomed Display mode.