I increased the size of the main image on my site by 32%. The image looked a lot better on a laptop, but on the PC the image stretched passed the max width of the browser (and was too big vertically to look good too).
It's probably the pixel density that is closer on the Laptop so it gives the illusion of a sharper image. Typically you also sit closer to a tiny screen that a larger one. Also it might depend upon what units you are using in your CSS if you are defining dimensions via a web page, etc.