While it’s widely accepted that Apple’s upcoming iPhone 6 models will come in two different sizes, including a 4.7-inch model and a 5.5-inch version, it’s still not clear what resolution Apple will use for its bigger iPhone screens. So far, leaks have detailed two potential resolutions for the iPhone 6, including 1704 x 960 and 1472 x 828, but well-known Apple blogger and insider John Gruber wrote a lengthy analysis on his website Daring Fireball, making the case for what resolutions Apple should choose for the bigger iPhones.
According to Gruber, who claims that he doesn’t have any inside information on the resolution he proposes, the 4.7-inch iPhone 6 should have a 1334 x 750-pixel resolution (326 PPI), while the 5.5-inch iPhone 6 should have a 2208 x 1242-pixel (461 PPI) display.
Gruber explains that Apple must achieve three things with its bigger iPhones including showing more content on the display at once, make the content on the display physically larger, and (crucially) offering at least the same display crispness as previous models if not better.
In his analysis, Gruber also dismantled the previously reported resolution choices for Apple, arguing that a 4.7-inch display with 1704 x 960 resolution would only display content bigger, not showing anything else on the screen on top of what a 4.0-inch iPhone can display. On a 5.5-inch screen, the same resolution will display “comically large” content, with UI elements being even bigger than on the iPad.
The 1472 x 828 resolution is “too small for 4.7, too crude for 5.5,” Gruber says. At that resolution, the 4.7-inch display would render objects smaller than on the iPhone 5 family. The resolution “works” on a 5.5-inch display, but the pixel-per-inch (PPI) ratio would drop to “only” 307, which is awfully close to the 300 PPI that Apple deems Retina worthy.
Thus, the only resolutions that work are 1334 x 750 and 2208 x 1242 for the 4.7-inch and 5.5-inch iPhone 6 models, respectively, Gruber argues in his detailed report (available at the source link) in which he also explains the app- and display-related reasoning behind his choice for these particular numbers.