If you are getting the gti to drive it properly then it has to be manual. Dsg just isn't as engaging as a proper manual and. Not really sure your lose anything with a manual and ACC either.
I say this as a big fan of the manual gearbox - I've owned various performance Golfs with manual - but that's a load of nonsense.
You lose most of the benefits of ACC with the manual box. With DSG it will keep pace with the car in front. Stop/start traffic in particular is a breeze, car drives itself. No changing gears / clutch work to keep the car in the right gear as ACC adjusts the speed.
As for "driving it properly"... there's not much out there that's more satisfying than racing through the gears with the paddles, listening to the exhaust pop as you do so. And then there's Launch Control...