Officially, the fastest accelerating hybrid--in terms of production cars--is the Infiniti, which has 350 horsepower on tap, a 0-62 mph time of 5.5 seconds, and a Guinness World Record under its belt.
The Panamera S Hybrid, on the other hand, has an output of 380 horsepower and will do the 0-62 mph sprint in 6.0 seconds flat. That figure is the official one from Porsche, though automakers are known to understate their figures on occasion.
As for the 2013 Lexus GS 450h, which is rated at 338 horsepower, Lexus says its hybrid setup is good for 0-62 mph acceleration in under 6.0 seconds. However, the car is yet to go on sale so may not be a contender at all.
Of course, the outcome of the upcoming drag race will soon be moot as there are several hybrid supercars in the pipeline all with projected acceleration figures under 5.0 seconds. Some that come to mind include the BMW i8, Porsche 918 Spyder and a possible hybrid Evo XI from Mitsubishi.