Coticules has a unique way of cutting steel. The garnets scoop the metal away rather than carve into the steel. This leaves a different edge. Coticules leave an edge that is very gentle on the skin, but they are not laser sharp like pastes orthe synthetic stones.
the edge from a coticule kind of pops the hair on your face rather than glides through like butter. Some like it and others don't. Its a ymmv thing.

I think most barbers use to like coticules because the likelihood of a cut on a customer was lessoned.