Combination of both. 55 and my eyes are fading so I use a 10x lupe but I find scanning and using mostly Photoshop better, especially on the back of the stamp. By playing with contrast and brightness, thins, inclusions, hinge remnants, gum disturbances and watermarks are much more clearly visible. Also check perfs and centering. I do this with any stamps I am looking to buy on
ebay or at auction. I also use a PDF program, Bluebeam, that I used in construction. I'll check out Linux.