While I am not too up-to-date about the 997 Series, I know for a fact that the 996 C4S/C4S cabriolets were noticebly slower than their 2WD counterparts, that was because they were wider(heavier) and had the 4WD system which also added weight - and most importantly, the engine was the same. These points are still true on the 997.
Given the engine being equal, it is physically impossible to make a wider (more drag (negligible but worth mentioning) heavier (4WD/etc) car perform the same as the smaller, lighter 2WD version. The fact that Porsche claims they do is marketing malarkey.
These differences became very apparent on the track with similar drivers lining up. The track has a way of amplifying a car's positives AND negatives.
But off the track - which is where most of these cars will spend the majority of their lifetimes, such things may not matter much to the average buyer. 4WD is very nice to have in a rainstorm
The marketing tactics shouldn't have everyone crying foul, but I find it neccessary to alert readers who care (ie, those who bother to browse/read threads like this) that they should not rely too heavily on information being given to them by a company whose best interests may not be to divulge true performance info.
With the 911 being the defacto sports car choice in its price range, it ends up competing with itself with very few outside rivals. That explains almost 99% of how and why Porsche advertises/specifies/positions their models against eachother (and with such precision as only the germans can manage).