Here is the whole truth. With no disrespect Kent o hose who have come or been doing this before me.
A rotary extractor is not needed but maybe 15-25 percent of the time and this is based on your client demographics of course so it will vary based on yours.
No tool does the final digging like a rotary extractor regardless of what scrubbed the carpet before extraction. Not a spinner tool, not a wand, not a drag wand, nothing like a rotary. The rotary has the contact/agitation and the shear number of cleaning passes. There is no contest when the rotary is actually necessary or SHOULD BE USED.