"Sharper display" refers to a higher level of clarity and detail in the way an image or text is shown on a screen. It means that the picture or text appears clearer and more defined, making it easier to see and read. Full definition
The size increase, extra camera functions, longer battery life and potential for sharper display images mean an extra # 120 on top of the standard model though. (pocket-lint.com)
The phone has a tad sharper display as the pixel density is higher. (sammobile.com)
Seriously, the only reason why you might choose to buy the Pixel is for that brilliant camera, and maybe the slightly sharper display. (themrphone.com)