DSC compensates for loss of traction by either braking one of the wheels and/or by backing off of the gas. On the street it should always be on.
For racing, autocrossing, etc. better drivers should prefer to have it off because they should be able to handle traction issues without slowing the car down.
I have found that making a rapid (speed) shift from 2nd gear to 3rd gear caused the ACS in my Cooper S to cut in causing quite a hesitation.