I think the main advantage of variable pitch quadcopters is the ability to change the thrust of each motor more quickly. You don’t need to wait for a motor to s

I think the main advantage of variable pitch quadcopters is the ability to change the thrust of each motor more quickly. You don’t need to wait for a motor to speed up, you just slam on the pitch of the blades and the rotational momentum in the blades gives you zero-latency thrust (meanwhile the motor is spooling up to prevent the rotation speed from dropping too much). Of course, you’re also right that the aircraft can decelerate faster, since each rotor can thrust in either direction (the same effect that allows for flying upside down and accelerating toward the ground faster than 1g). Lastly, I assume that variable pitch quadcopters are able to autorotate in the event of a motor failure (not that that’s super important for relatively inexpensive unmanned aircraft).