The speed drive is always the right solution, when wanting there to be no extreme marginal values (neither a very high gear nor a very low one) but however when a wider more general gear ratio is desired.
high speed drive
The schlumpf high speed drive has a large gear transmission ratio and is suited to riding in very high gears (e.g. fast E bikes, bikes with small/thin wheels, recumbent sports bikes and velomobiles).
With the schlumpf mountain drive you gain additional very low gears which enable you go climb the most extreme inclines easily.
the schlumpf rehab drive reduces to very low gears helping you to master the most extreme ascents without a struggle. Built into rehab bicycles, handcycles, or trikes, this kind of gear is easily shiftable under load or while standing still.