There are three settings for the DSC (on, partially on, off). By pressing the DSC button once you switch to partially on. By pressing the button for 3-5 seconds, it will turn it off.
It only makes sense to turn it off if you would like use launch control or take off faster at the light. With DSC on the car reduces the torque on the wheels at start, thus you can experience a lag in the acceleration.
This video is in German, but they illustrate the difference in acceleration with/without DSC (skip to circa 5 mins):