Check out the individual reviews for more information, and since eyesight is an entirely personal thing, we'd recommend going into an Apple store, or checking out a friend's Retina and non-Retina devices (side by side if possible) to see the difference for yourself. You may not even notice one, in which case your buying decision just got easier.
What are Retina and Retina HD displays, and are they worth the money?
What about Retina HD? That's harder to quantify, since the iPhone 6 and iPhone 6 Plus are such different propositions. They're lovely screens, for sure, but the main thing they offer over their non-Retina predecessors is size. The iPhone 6 Plus is super, super sharp, but the iPhone 6 has the same pixel density as the iPhone 5s.
Other than the higher resolution that comes with the larger screens, our (totally subjective) feeling is that the additional 'Retina HD' criteria mentioned above are the least of the reasons why you'd be upgrading from your iPhone 5s - the polariser is quite nice for sunny days, the viewing angles seem to be very slightly better but will hardly affect your day-to-day experience, and the improved contrast hasn't blown us away. But then, the improved camera, bigger screen, redesigned chassis and Apple Pay will be what most potential upgraders are interested in, not the differences between Retina and Retina HD.
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