For every 20mm jump in rotor size, the mechanical power increase is 14%. This means that going from a 180mm rotor to a 220mm rotor would boost system power by 28%. But too big of a rotor could also lead to not enough heat being generated, and a smaller rotor where the correct amount of heat is being generated could actually have more power on the trail. Paying attention to the color of the spokes on your rotors (below the pad track) can be a tell of how your rotors are performing.
-Browned or bronzed discoloring means the size is optimal.
-Purple or rainbow discoloring means your rotors are running too hot and sizing up would be suggested.
-No distinct coloring would suggest they aren't getting hot enough and sizing down would lead to optimal performance.