It isn't. The 911 is just far more efficient. For one, it weighs 1000 pounds less. Secondly, the all wheel drive system allows it to actually put its power down off the line. Finally, the PDK shift speed can not be beat.
The Charger loses running 11.833 to the C4S 11.671 pass. The trap speeds are not provided but sometimes having more power is pointless if you can't actually use it.