To me quality applies to a few categories;
How true to the morph it is (what it looks like compared to your idea of what you look for in that morph)
How healthy the animal is (should be a given but not always)
Size of the animal compared to its age (not power fed or under fed)
Feeding response (an animal that has the best of the other categories but fails at this one is a deal breaker for me, picky or poor eaters are the worst IMO)
There are probably other things I look for but cant think of at the moment but those are the big ones for me.