DisplayMate is a company that sells software to calibrate and optimize computer displays. The company has posted a series of articles comparing the new higher resolution displays found in smartphones can computer tablets. See the reviews here http://www.displaymate.com/mobile.html
One of the interesting points made in the articles is that the Apple's "Retina" display resolution of about 325 pixels per inch is not at the limit of the human eye's ability to resolve points of light. Holding a phone at a distance of 10 inches, people with the best vision (20/10) can resolve individual points down to about 600 dots per inch. When the phone is held closer than 10 inches, people with normal vision (20/20) or well-corrected vision can often see resolutions approaching 600 dots per inch.
The newest smartphones, with Full HD display (1920x1080), have about 440 dots per inch. At normal viewing distances, most people should be able to see the difference between an Apple "Retina" display and one of the newer Full HD displays.
One of the interesting points made in the articles is that the Apple's "Retina" display resolution of about 325 pixels per inch is not at the limit of the human eye's ability to resolve points of light. Holding a phone at a distance of 10 inches, people with the best vision (20/10) can resolve individual points down to about 600 dots per inch. When the phone is held closer than 10 inches, people with normal vision (20/20) or well-corrected vision can often see resolutions approaching 600 dots per inch.
The newest smartphones, with Full HD display (1920x1080), have about 440 dots per inch. At normal viewing distances, most people should be able to see the difference between an Apple "Retina" display and one of the newer Full HD displays.