All the supercharger guys keep talking about lag. Turbo lag was something that happened with turbos 20 years ago or if you chose a poorly matched turbo. I will admit if I am at 1500 rpm in 5th gear the jrsc will will have more power available, but that is why God put a shifter in the car.

The superior power output of the turbo is all a matter of efficiency. If both a turbo and a supercharged engine are making 7psi boost the cylinder produces a given amount of work. A portion of that work is goes to turning the crankshaft and the rest is rejected as heat and exhaust mass flow. All the power used to drive the supercharger comes from the crankshaft, robbing the engine of power output. The turbocharged engine for the most part uses the exhaust energy that is normally thrown overboard to drive the compressor. The crankshaft gets to give more power to the wheels.

Also good centrifugal blowers are more efficient than any of the rootes or screw type blowers. This results in lower intake manifold temperatures for the turbocharged engine which gives better power and is easier on the engine. Also installing an intercooler on a jrsc system is very difficult or impossible.

A supercharged system is also always limited by the fact that the output of the SC is fixed by being driven at a speed that is always proportional to the engine speed. So to get more boost you have to change pulleys? This especially bad with belt driven centrifugal SC's were boost is not linear to the driven speed. Those type of systems really have poor low speed performance.

For the turbo engine boost very easily adjustable and with electronic controllers a boost curve can be configured anyway you want it.

As four stroke engines technology continues everything will go to turbocharging and nothing will be supercharged.