Always used M185 (very handy). But (especially at night) the household was annoyed by loud "clicking". M220 compared to M185, one might say, silent. I am very pleased, others - too. The M185 has one more drawback - the scroll wheel starts to "go crazy" after 1.5-2 years of use (I cleaned it, changed the batteries - nothing helps). I changed 7 mice because of this. After another incident with the M185, I thought it was worth trying something else. M220/M221 - same but much quieter. Let's see how it behaves in the long run - I hope that I did not make a mistake in choosing.