The Magnuson unit is actually called a Hybrid Roots lobe or Twin Vortices Series design. It is a combination between the traditional Roots system (designed in the 1860's) and the more modern Lysholm Helical Screw System (designed in the late 19th early 20th centuries)-- both are positive displacement designs and the real difference is that Roots units actually doesn't increase the pressure inside the unit. That has to be done with in the cylinder head. Where as a twin rotary screw unit does compress the air within it. Also the Twin Rotary Screw systems show less parasitic drag because they are more efficient and usually require less power to operate when compared to a roots unit.

The Ripp is a simple Centrifugal System-- basically they became popular in the 1930's when supercharging aircraft engines. They basically are just turbo-superchargers that replace the rear impeller with a drive shaft and gearing unit that directly drives from the engine. These are probably the best unit to use for two reasons: One they require little horsepower to really operate because of their small size and high speed operation. They are also are the most flexible-- you can get them with a hi-low range or even a combination of hi-low and 2-stage units if you are so inclined to do so. Those are features that you cannot get on roots or twin screw unit.

However, if you're going to spend the money-- I say use sequential turbo-superchargers... With a properly mated system you can eliminate turbo lag and produce massive horsepower with very little back pressure on the engine. It is about as free as one can get.

But no matter the system-- water methanol injection would really improve the performance overall with any fuel source.