You did seem to be suggesting that someone was advertising 'maintenance' cleaning by using a portable.
As I've mentioned before, in my personal experience, which is considerable, the best result I've personally achieved, have been through the use of a CFR machine, with 400psi, but surprisingly, fairly low vacuum power.
The design of the tools allows the operator to dwell on areas of heavy soiling without soaking, this results in, I believe the finest restoration clean possible, comparable with, or superior to any other wet extraction system.
Only my opinion, of course, but based on experience and experimentation.
However!
An accomplished operator, with another system and possibly newer technology, may well be capable of similar results.
What c/c's should do, if seeking to be 'among the best' is to attend live demo's of all systems to allow an informed decision to be arrived at.
If you can't find such demo's, contact suppliers. They want to impress you and you will learn a lot in the process.
I should perhaps add, that my c/c days are mainly in the past and only carry out a low volume of work, due to a knackered body and other comittments.
Don't expect miracles from machinery, simply because it's got massive power, or high heat, or whatever.
It's still the person at the end of the wand who determines the result and this takes, discipline, dedication and a genuine desire to deliver a high standard of service.
Happy days
r m