And QHD is stupid on a phone. 1080p is a bit of overkill honestly, but it makes sense given the competition. I'm perfectly fine with the resolution on the 4.7" too. (I've never had a complaint about the pixel density on my iPhones.)
I've seen plenty of 1080p screens on smartphones. Is there a (small) difference? Yeah. Does it impact my life in any meaningful way at all? No. Everything is very clear on my 5S and retina mini. No need to be much sharper than that. I'd rather have the better battery life than the higher resolution screen. (for the same form factor).
I have both sitting in front of me. While I can see the 2013 Moto X screen just fine (which is retina quality), it is nowhere near as clear, crisp or colorful as the Nexus 5 at 1080p. You are fooling yourself if you believe there is little difference and that 326ppi on a 4.7" phone is acceptable for the price you have to spend!
Superficially looking at how Apple presented the two, it seems like it's the Plus that is going to be their main focus. So it could be suggested, very prematurily and without evidence to support it, that the 6 is going to be the low end version, while the "real deal" would be the 6 Plus.
Which is a hilarious move.
Ok, well, first of all, the Apple screens are better than the Moto X screen in quality (IPS, etc). Second, I have a 326 ppi phone right in front of me. I know exactly what the resolution is, and it's perfectly fine. So many people get so bent out of shape if there is something out there that is 'better' that they lose sight of whether it matters that it's better. If it matters to you, go for it. It doesn't to me. At all.