Hi Duncan
I find that, from the machines I've had, played with and seen demo'd, the Scorpion is up there with the best of them. If you run the 2" vac hose rather than the more convenient 1.5" the vacuum performance is, by porty standards, awesome. As the Scorpion is set up for maximum airflow, it makes good advantage of the 2" hose. Many of the other high performance portables are set up for maximum vacuum lift. These would probably not have any gains with the T/M spec 2" vac hose. They may even be at a disadvantage.
I would suspect that you would never need 500psi with conventional tooling, but may find an advantage with something like a CFR Wonder wand.
The only thing I am wary of with the Scorpion machines is that they have protruding fittings at the sides. I would expect an owner operator to take this into account when moving and loading the machine. A less considerate employee could well be careless and knock these off.
When it comes to heat, there are many with extremely varying views. Mine is that cleaning is about a whole system, not just a single component. If you get the vaccing, pre-conditioning, agitation and dwell time right, your HWE machine is then used purely for rinsing away the loosened soil, so heat is not such an important consideration. Heats biggest advantage in this scenario is with the pre-conditioning. With the final rinse, high heat will improve the first few seconds of moisture evaporation from the carpet, but then the advantage is lost. I work with hand hot water from the tap, if available, but a cold water rinse doesn't lose me any sleep. You can always use an in-line heater if required with your chosen cleaning solutions.
A facility you have with the Scorpion is to add the large capacity in-van tanks should you desire to have a truly demountable truck based system. This can be added at any time subject to cash flow.
Safe and happy cleaning
Ken