reduces your margin of error allowance, thats all. That is of course, except for the way it limits wheelspin. Assume for a moment that you already know that part...If the car was, say, to get sideways because you stabbed the brakes and sharply steered, I don't think it would help you out. However, keeping the DSC on does provide the beginner driver (or one who is new to FWD car peculiarities) more stability if the driver makes mistakes in handling a turn, or if the road is slippery. IT DOES NOT save your ass, however.
Case in point, about 2 days into ownership, I took a U-turn type on-ramp to the highway. I had the DSC OFF I did it at about 50mph, and let the car slow down via drivetrain and engine compression resistance. About the moment I was at the apex of this hairpin, heading slightly downhill, I tapped the brake and the car rotated its ass around predictably, yet quickly. Because thats what I expected, it was uneventful if not quite a bit of fun. I recently did the same maneuver, this time w/ the DSC ON, and the car kicked in all sorts of braking tricks to prevent the rotation, ending up in a mildly understeering turn that was also uneventful.
In essence, if its playtime, then turn it off, but expect to be able to handle the car correctly if an emergency lane change, or a hard brake maneuver is needed. I turn it off whenever I'm in "GO" mode, and leave it on when I'm in no mood to play.