I will give you an example. If the you command an acceleration during climb, the autopilot accelerates to that speed and instead of smoothly pitching up to climb, it agressively pitches up. On the otherhand, during descent, if ATC tells you to reduce speed, the autopilot is not assertive enough during a level change descent. It will maintain a certain V/S and the airspeed itself will decrease very slowly requiring either a speedbrake or V/S intervention from the pilot.