They're better at using friction to cut through things, and if the flakes that get sent out are too large, or aren't cleanly seperated, they gum up the mechanisms.
Tl;dr, chainsaws rely on the thing they're cutting into being firm and sturdy so they can saw through it easily via friction and a minimal cutting edge. Against things that tear, their blade is still dangerous, but will rapidly lose effectiveness.
This makes sense considering how the chainsaw blade design was originally designed for cutting through human bone, iirc.

