Earlier quoted context omitted.
Really? Your eye can resolve the difference between 300 ppi and 500 ppi at arm's length? Also, don't be a stranger.
You use your phone at arms length? I am usually holding mine at like 6 inches to 1 foot from my face. I could very much tell the difference between the 318 ppi of the nexus 4 vs the 445 ppi of the nexus 5 with my usage patterns. I am skeptical that I would notice further improvements though.
Perhaps screen brightness also impacts this - do you run f.lux?