I have never compared the RPM of an engine cranking with a direct-drive starter vs. a PMGR starter. My suspicion is that the engine does crank slower with the PMGR starter, but not much slower.
Electricity going through a direct drive starter has to power the armature windings AND the field-coil windings. Electricity going to a PMGR starter powers only the armature, the "field" is a permanent magnet not an electromagnet.
A smaller armature getting the full voltage/less resistance of not having to share power with the field coils no doubt spins faster than the old-style starters.
A s a side-bonus, the PMGR starters take less amperage to spin the engine. Less amperage load on the battery means they tend to receive higher voltage, again helping them to spin faster.
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