My criterion for a lens to get anatomical detail from the portraits or few meters faraway human subjects. Skin details , muscles like an Greek sculpture drapery and below the skin the blood flow. For that color saturation , I test the subjects under oldest technology light bulbs at night. I must see the clean red blood flow and green blood flow. I only get this result from Leica lenses , especially Summitar. And my Rollei 35S with Sonnar 40 have a similar nature.
When it comes to scanning and dpi thing , I hate that stuff. I dont think their printers are not well calibrated and free charts would print bad. Buying a chart is more expensive than original Leica .