he's right, there is more than one type, positive displacement gives it a much broader spectrum.

you have to realize, both have their good and bad positive displacement means your pretty much getting full boost as soon as your on it, and in a perfect world, full boost at idle.

centrifical blowers are like belt driven turbos...more commonly have flat torque curves and linear power bands, they do produce a fair amount of heat. but honestly, a centrifical blower on an automatic big stall, high shift extension car will hold full boost or close to it an entire pass.

i cant justify supercharging a 4cyl due to the fact, it takes 120hp to spin a t-trim to 50,000RPM