I think the Powertorque I'd the ultimate one purpose engine specially developed for it's original task: to drive a flywheel of a certain mass directly and nothing else. My theory. FCs were used in more applications.
The Powertorque was used in the tilt-a-cut. How were they? Maybe they were slightly retuned as was the 600?

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!