Well, considering Insideline's review of the BRZ on the dyno revealed a massive torque hole in the 4000rpm area, a S/C would be more helpful in overcoming that in DD. On the track, you just have to keep the revs high (this FA apparently loves this) to keep out of the hole. But a turbo helps out well in that scenario too.
Speaking of S/C, I found this article on Autos.ca (CDN driving mag), that talks about a variable speed S/C, that adjusts boost flow so that there isn't the parasitic loss at idle/low speeds that eats up MPGs. Check out the read.
Fallbrook Technologies soliciting select OEMs to adopt a variable speed supercharger