I think the roots-type or centrifugal superchargers are both relatively efficient. The roots-type definitely makes the most heat, but a twin-screw SC will actually consume power at low rpms when it isn't boosting.
EDIT: Forgot some stuff. A centrifugal SC creates less heat, but it also isn't very good at making power at low-to-mid rpms, so the power it creates is at the top of the revs. While it may technically be more efficient than a roots-type blower, that doesn't account for the usability of the delivered power.