What is the difference between Baratza Burrs S1 and S2?

The difference in the burrs as you can see in the image is that the S2 burr upper teeth (cutting surface) (photo on the right), is flatter than the S1 burr which has sharper pointed upper teeth (photo on the left). This variation in the cutting surface of the burrs is what creates the grind differences on the fine to coarse continuum. The S2 is developed for better grinding at a coarser level, thus better for pour-over brewing methods.