Yes PDK is a sequential gear box but it cannot really be compared to a racing sequential gear box where one still has to use the clutch pedal for take off and downshifting.. PDK is as smooth as an auto box, just shifts quicker. A racing sequential gear box makes your neck crack each time u dont use it at the exact rpm...
a racing gear box doesnt have a D mode where one can just cruise off. Just cant be compared with each other.
From my point of view a sporty stick shift like in the GT3 is closer to a racing sequential gear box than PDK, which to me is much closer to a perfectly working automatic gear box than it is to a sporty one. 0-60 times dont count when it comes to track performance...