[acqq]

So what is then the rationale for the "bigger" variant not being also 326 DPI? That would give something like 1562 x 878 display for the 5.5 inch one. Less pixels, therefore faster. The difference between 326 and 461 DPI is most probably not discernible for most of the people.

Another advantage: not needing one more target resolution of the resources. And another: no need for the new scale for the pixel masks by production.

[LazyGhost]

Gruber does mention his rationale for not using a resolution that's close to this. Under "Other Resolutions" he says:

  1564 × 880 is feasible for a 5.5-inch phone.
  That’s what you get if you maintain the 326
  pixels-per-inch density and @2x scale. This
  would increase area — the number of points
  displayed on screen — by a whopping 89 percent.
  But it wouldn’t increase the size of what you
  see at all. I think the sweet spot for a
  5.5-inch phone requires you see to more content
  and to make what you see at least a little bit
  bigger. So that’s why I’d bet against 1564 × 880.
 (1564 × 880 would be implausible for the 4.7-inch
  phone: it would render UI elements and text 15
  percent smaller than all previous iPhones.)

[acqq]

Thanks. To "see more content" is actually fulfilled with 1564 × 880. To "make what you see at least a little bit bigger" (seems he thinks that the icons and the text should be visually bigger when holding the phone in front of you at the same distance as before? why? it's still a phone) results either in needing the new resources or leaving the pixel perfectness (which won't happen for Apple) -- I don't buy it. But let's see if he actually got the insider information about something so non-obvious.