@ger21,
After reading Nick’s post, I did a bit of digging around, and came across the Super-PID. I thought to myself that it must have been quite a trick to miniaturise all that circuitry, into a module that fits inside a router housing. From what I understood, your Super-PID controller has an infra-red sensor, which is triggered by a reflective spot (I assume painted on to the shaft?). I gather some other types have a Hall-effect sensor, triggered every time a magnetic strip on the shaft goes past. As you say, this is a true rpm-based controller.
I could not get more clarity than that. It looked like a De Walt (611?) might have such a controller built-in, but a lot of guys seemed to want to replace it with the Super-PID, so I am completely uncertain.
But if, as you and I both seem to think, the average VS router does not have such a feedback loop, the controller is then a relatively simple solid-state device (or two: a diac and a triac). I cannot see why there should be a difference in performance between an inboard and outboard controller. In principle, such controllers allow the motor to draw current up to the design maximum (if not more), when the motor is forced to slow. The circuit does not “increase the power” as such. The extra current increases the torque, sometimes allowing the speed to increase again.
I suppose there is some current limiting circuitry to prevent motor burn-out in a total stall - this may impact torque.
Just my thoughts - remember where they come from.