Regular auto uses fluid and torque converter to take up the slack so to speak. It's always in gear when stopped and foot on the brake.
The DSG is a manual but automated. When at a stop, it is not in drive if your foot is on the brake. Same as a manual car, it is in Neutral or the car would die if the clutch was engaged and you were in gear.
Launch control on DSG basically drops the clutch at whatever rpm it's set for. When your foot is on the brake, it is always in neutral though. That's why you always get a bit of hesitation when letting off the brake on a dsg.
Not sure how regular autos and launch controls work on these newer cars.
Thanks that was an easy to understand explanation. My next car will be a GTI w/DSG I hope.