Turbo's tend to be more expensive, but also tend to be more effecient.
Turbo's have lag caused by the need for exhaust air to run it, so the addition of power is initially delayed during acceleration. This can benefit a FWD car since it is more difficult to maintain traction under had acceleration.
Superchargers run off the engine's belt, so the boost is always present. However, since the supercharger is powered by the rotation of the crank, a portion of the power gained is lost due to the additional resistence the motor must over come to drive the supercharger.
There are many pros and cons for either setup, but if I were going to add either, on I would opt for a turbo w/ an intercooler and adjustable wastegate. Along with a programable chip and MAF, high lb. injectors... etc...
