Howdo lad - I am interested to know what you mean by "faster". Bearing in mind your new car has DSG and has four wheel drive so I can imagine it would definitely be faster in;
1) Wet
2) Low speed accelaration
3) Through the gears
4) Coming out of a sharp corner under full power
However from experience having been on a track on the same day as a Golf R DSG with approx 60bhp power than my car (and an interior and luggage that mine never had), the lap times were about the same from what I have been told. Obviously that was on a dry day and ideal conditions.
I am not as blinkered and naive to say that the Leon is more capable, but I would think under certain circumstances, the Leon would be faster.
1) High speed accelaration
2) Top speed
3) Fast cornering
Look at certain classes in rallying to see similar spec cars with 2 wheel drive beating 4 wheel drive cars through some stages as an example.
As you know my next car, I hope, will have four wheel drive, and I would have a DSG Golf over my manual Leon any day but I wouldn't say the Golf was faster than the Leon in every set of circumstances
PS - For what it's worth, my bet is that with those two cars, VAG will have made sure the Golf arrived on that track with more than the claimed bhp (certainly more power than the Leon did) to ensure it beat the Leon to justify its status and the extra coin to buy it. As mentioned above though, the way the Golf behaved on the track with its extra weight and extra drive train losses and with it being dry and the Leon not wheelspinning, and both cars having a manual box, it seems to me something was rigged.