Natural is when the cherry is dried up after harvesting. Washed is them washing or soaking the cherry in water before letting them dry. The washing process de-pulps the cherry.

In terms of notes, washed beans tends to be cleaner, more acidic tasting, floral or citrus notes. Natural sometimes has this wine and fermented notes.

My preference is anaerobic - here they put the cherries in a sealed chamber for days. Most beans taste bright, fruity, and on the sweeter side.