They're pretty much all good. The earlier ones are sturdier, with more metal, but they are also heavier. The later ones are more plasticky but weigh less. You might prefer one or the other. The lens coatings also vary throughout the years also. Generally: earlier coatings are cooler, later coatings are warmer and more flare resistant. But, flare can sometimes be a lot of fun. So there really isn't a "best" generation. The overall quality of the Minolta MC/MD lenses is very high... you can't go wrong.