Beyond if the legends are all clean looking while being placed properly & all the caps fitting & sitting how they are supposed to. Looking at the underside & how clean or sloppy the double/tripleshot is, is a good indicator of quality. Is there any flashing present in any of the caps is another good indicator (flashing is when you see a line where the molten plastic came together. If the temp is too low it allows for the plastics to not blend together well), then how big & visible the sprue marks are is another indicator of quality I will use to judge the overall quality of any double/tripleshot keycaps. The same holds true for dyesubbed & UV printed caps, but I tend to be a little more forging with the printed legends compared to double/tripleshot legends.

Thank you very much for the explanation. Is the harshness (or edge sharpness) of the keycaps edge something that people care about?

No problem, some people care about the sharpness/smoothness of the corners but I would put that down to more a preference thing. Unless the cap is wonky looking or something cause of its edges.