I agree that the fun factor makes RWD a better choice. However, from a pure drag race perspective, AWD is just better performance. I'm not trying to argue with anyone, however, when Motor Trend rolls out an obvious Audi cheater car and tests it against a rwd B7 (for which we know to be slower than xdrive)...something's not right.
The highest performance Porsche sold in the US right now now is the 911 Turbo S which utilizes AWD 60/40 rear wheel bias. (Only available in AWD).
As far as the weight argument, the weight spec difference in the F01 is an additional 35 kg for xDrive which is why the acceleration numbers are better for the xDrive.
Sure, RWD is more fun but if you want pure acceleration performance from a standstill, AWD is where it's at.