The best way to compare image quality depends upon the individual preferences. If you prefer to compare details of both images, then click on 'details' and get information like name, size, type, and last modified date. For side-by-side analysis, click on the 'slide' button. If you want to blend images and want to compare images, then click on the 'fade' button. For pixel level comparison, click on 'pixel match' which gives differences in the number of pixels and highlights with colors of your choice.