I have 50mm and 90mm Apo-Rodagons and a 150mm Apo-Componon. I think the 150 is probably the best of the lot, but only because it is of the most recent vintage of the three. They are all excellent. They all should have some incremental improvements, so if you have a choice between two used lenses of the same focal length, you might just pick the newest one or the one in better condition.