It depends on what kind of power you want. A supercharger provides more low end torque. This is good if you plan on autocross where you are constantly turning and downshifting into lower RPMs. A turbo provides much more peak HP which is better for straight line drag strip acceleration. Turbo lag can be greatly reduced if you use a smaller, quicker spooling turbo, but these smaller turbos don't produce the as much peak horsepower.