I read that screw is the most powerful, but with the most losses. This is nothing to do with efficiencu however.

I think for light applications centrifugal is best. Low loss, but low output.

A car's supercharger might require 100bhp to rotate it at full speed, however it releses 200bhp, so you gain 100 extra. Efficiency is therfore the ratio of energy used to energy released.