It's funny really. It used to be all anyone seemed to care about were the corners. Then with the advent of the registry and since PSA is all about centering, that became a major focus. As someone else said, there is no right or wrong. But to me it all boils down to eye appeal. If a card is majorly off center and just looks bad, I probably won't want it. But if it grades out at as a PSA/SGC 1, but just has some minor paper loss on the back and looks beautiful, I'll take it. That's just my preference.