This is a battle of modern hybrid technological efficiency against raw brute strength. So who wins? The 1200 horsepower quad turbo sixteen cylinder all wheel drive dual clutch monster wins. However, not by much. The Porsche 918 Spyder has the more efficient drivetrain with its two electric motors and 4.6 liter V8 (887 horsepower combined output) losing the drag race by only a tenth of a second.
Results in text form are here, expect a video from Road and Track once they are finished editing it but it is very cool of them to share the data early:
Two miles an hour slower for the 918 Spyder through the 1/4 mile and a tenth of a second less in elapsed time yet it matches the 0-60 figure thanks to the instant torque from the electric motors up front. It does this with 313 less horsepower, superior handling, a lower curb weight, and much greater fuel efficiency. The Porsche 918 is really the more impressive engineering achievement. Yes, the Veyron SS does have the higher top speed and will always ultimately 'win' on the top end so to speak.
Regardless, the McLaren P1 beats both of them and appears to be the king of the newest supercar crop.