I don't know if the Thermaxes I had in my collection-sold them to a vac place that needed them for parts-The suction of the machine didn't impress me one bit-why I got rid of them-I could generate more suction and airflow by inhaling thru its hose!It seems like the unit really isn't a vacuum-but an upolstry and furniture cleaning machine.
I am not familiar with any of these except The Rainbow, however, from what I have heard the other machines use baffles where the Rainbow uses the seperator. I would judge in the long term the Rainbow would be the winner.
I am in love with my Thermax. I put it up to the tester and it had a little more suction than my Rainbow D4 and my newer Hyla.
I don't know anything about the new Thermax, mine is an AF1. I have had so many people want to borrow it that I decided to become a dealer for them. Have not finished the paper work on it yet but getting there. No one has them here in the Midwest.
However I still would rather have a paper bag VS water.