The above is a brief overview of how the different resolutions compare with one another. Obviously, the more dense your pixels are, the more beautiful your screen and the displays within the screen get. Ultra HD 4k is the best, with the most pixels per inch, and is also the largest of them all. Everything will seem extra clear for you.
Check out that awesome picture above, displaying Metro Last Light in both 4k and the standard 1080p (which is considered Full HD. It may seem subtle to all, but this zoomed in picture shows just how beautiful 4K really is. It makes a large improvement over already good graphics.