Just to clarify, twin screws are more efficient... period. Not just for race applications or just for the drag strip. They are just more efficient. Across the board, they are the better designed supercharger. To say they are more efficient for race applications is cutting them short. They produce more boost per revolution, produce less heat per PSI of boost produced, and don't fall flat on their face in higher RPMs. All in all, they are the better blower.
I'm in California and plan to keep my 4Runner for a long while, hence I need a CARB approved supercharger. That's the only reason I chose the Magnuson over the whipple.