A small turbo could do well also, if you can keep it spooled during the times you'll need it. Most of that will come down to engine load. A supercharger is nice also though, but I agree that all motor is pretty sick too. The answer is that all of the options can be made to work (and work well) if properly done.

If this car will be used for anything other than autocross, for example street driving, I'd choose the option that will make you happiest on the street. I'm not a firm believer in optimizing cars for autocross use if that compromises the other uses for the car. So if you want a powerful street car to run around town with, make a powerful street car to run around town with and then have fun autocrossing with it occasionally.