Two rumored developments about the larger of the two expected iPhone 6 models emerged this weekend. First, a 2915 mAh battery (85% larger than the one in the current iPhone 5S) was leaked that seems to fit with a previously leaked chipset that would fit the 5.5-inch form factor. Second, a Chinese website Apple Daily tipped that instead of being named the iPhone “Air,” the larger iPhone 6 will be dubbed the “6L”. If true, this information points to one under-explored issue about the new iPhones: screen resolution. Specifically, will the 4.7-inch iPhone 6 and the 5.5-inch iPhone 6L both have 960 pixels on the short side, or will the 6L bump up to the 1080 pixels required for 1080p HD video?

Back in May, Mark Gurman of 9to5Mac wrote a very convincing story about how the new larger iPhones would move from the 2x resolution of the retinal 4 and 5 series to a denser 3x resolution. According to Gurman, both new phones would have 1704 x 960 pixel screens, which works out to 416 pixels per inch on the 4.7″ model and 356 ppi on the 5.5″ model. His argument was that, like the iPad  and iPad Mini, these two different devices would share a common pixel count to make it easier for developers to deal with updating their apps for these new devices. So convincing was his story that little else has been said on the matter.

If we accept Gurman’s math, then the upsized battery on the 5.5″ 6L will serve to give it greater battery life (despite its larger screen size) than either the current iPhone 5S or the 4.7″ iPhone 6. And this would be a good thing because the primary activity of phablet users is watching video. So better battery life means more viewing time. And who doesn’t want that?

Just to play devils advocate for a moment, what if that extra screen size was used to make the 6L full 1080p HD? This would achieve parity with Samsung’s Galaxy S5 and Note 3. Most importantly, it would deliver full resolution for all of that video 6L users will be watching at a pixel density of 401 ppi, just under the 4.7″ model’s resolution. [An interesting side note, the next big Samsung smartphone is actually smaller than their current models with a lower pixel count. The just announced Galaxy Alpha will have a 4.7-inch screen with a pixel resolution of just 720 x 1280 pixels, 312 ppi.]

The power efficiencies of the new A8 chip in the iPhone 6 models should help offset the additional screen illumination and pixel computation demands. More importantly, changes in Apple's AAPL +1.38% best practices for building apps, including auto layout, multi-resolution mode and increased reliance on vector graphics should make the burden on developers far lighter if Apple were to introduce two new devices with different pixel dimensions.

The real issue is a three way optimization between how much better the user experience of full 1080p HD video is compared to the benefits of extended battery life compared to the benefit of larger touch targets on the larger screen. As with digital cameras, more megapixels don’t necessarily make better pictures. Undoubtably Apple has tested these variations and is confident that the iPhone 6L phablet lives up to its customers’ larger expectations.

UPDATE: I had a lively Twitter exchange with @GordonKelly this morning about whether Apple would really do this. Kelly tweeted “I can’t see Apple creating more confusion with 2 new resolutions.” The question for me is really “Confusion for developers vs UX for customers.” and it all comes down to, “how much better is 1080p on a phone?” At some point Apple will have to admit to the fragmentation of iOS and get beyond pixel multiples of the original iPhone screen, as conceptually neat as this may be. [3x is very different than 2x as far as conceptual neatness goes. 2x => 4x is easier for people to grok.] I contend that all of the pieces are now in place for iOS to size more dynamically, as Kelly points out Android has done for years. Could Apple make this shift now, with the 6L? Kelly tweets, “I don’t see it. Over complication (in this case with resolutions) is not an Apple trait.”