I agree with the above post. I run MDM in for the first session or until I'm warmed up and comfortable. Leaving DSC on is safer for the beginner obviously but you won't learn proper car control since the car is intervening. The M school guys will say to leave it on as well and to notice when it kicks in. This will show when you're overdriving. This is only at the beginner level since you need it off to rotate the car properly.
I leave it on for new tracks as well.
Having DSC or any traction control is new to me since my former track cars are a lotus Elise with none, a base 350z with none and a 240z.
Current: SBM X5d, SPEC E46 racecar, Black FJ Cruiser, 1970 240Z
Former: '11 MCB E90 M3, 2011 Lotus Exige, 2003 350Z, 2002 WRX, 1996 Supra turbo, 1984 320i, 1987 E28 M5