Impossible to answer such a question UNTIL you know:
1. What function the car will fulfill. Daily driver? Ocassional street/strip? SERIOUS prostreet/strip? Dedicated drag racer?
2. Even then, high horsepower numbers start to become meaningless - what counts (other than in a dyno contest) is how that power gets transfered to the ground. Putting out even 400hp at the rear wheels WITHOUT any upgrades to the wheels, tires, rear suspension, gears (and perhaps clutch and transmission) could easily mean that your times at the track will disappoint.
Only the individual knows WHAT they plan to do with the car - and the plan to achieve those goals should include a review of the ENTIRE automobile, not just the power plant.
But back on point, there are good REASONS why the OE manufacturers prefer the positive displacement blowers. This has to do with packaging (the fit and finish under the hood, and the ease of future maintenance and warranty coverage) and the fact that they build STREET cars meant to be driven every day and survive the rigors of that function. They match the desired powerband with the power-adder. Simple as that.
Those desiring something akin to an 03-04 Cobra or perhaps the LS9 powerplant in the bad-dog Corvette will be best served by looking to a twin screw positive displacement supercharger.
Change the emphasis to the drag strip, or to shooting for some sky-high mountain peak on a dyno chart, and the path will change - I would suggest a ProCharger, or a turbocharger (or 2), but again, that's just personal preference.
Its been my experience that the key ingredient rarely discussed is simple "impatience". The process needed to pile up sufficient cash to make the purchase - then to do the install - and THEN to get it all tuned - means that the twin screw (which costs more) often loses out simply because the critical mass of the bank account will match a simple VorTech install long before it hits the KenneBell line!