If your buying brand new, a turbo kit isnt gonna cost that much more then a supercharger.
The turbo is much better then a SC. SC's eat up power because they are belt driven. Because they run off a belt, they put alot of stress on the crank(well the centrifugal SC's do, not sure about KB's) which can cause your front crank bearing to go, or even snap your crank. This shouldnt be a big issue with moderate boost levels though.
A centrifugal sc builds boost with rpm, so you wont see full boost until 5500+ rpms. Where as a turbo uses the exhaust, and you can see full boost by 3k rpms. Which leaves way more "area under the curve".
Theres much more information on the subject. But which SC are you talking about, a centrifugal(vortech, paxton, ATI, powedyne) or a Kenne bell?