My own business is a combination of residential and commercial work. Probably 80% of my actual appointments are residential, but since commercial jobs are nearly always larger, commercial accounts for in the range of 40 - 45% of my annual gross $$.
I use the standard size Challenger for all of my residential work, backed up by an Oreck 12" Orbiter for small areas, large stairs, small stair landings, etc. I also use my Challenger on a lot of my small-to-medium size commercial jobs.
Also, my 6" orbital machine (part of my Package) is used on most stairs, as well as on upholstery.
I also carry a hand vac/porta-vac (Royal Dirt Devil Classic model) and a Kenmore Progressive upright vacuum.
I use this brand & model for its annual first place finish in the annual Consumer Reports "pet hair pick-up" category.
I've done commercial jobs of up to 40,000 sq. ft.
On large commercial jobs, I will mostly depend on my
Orbitec CX-20 and Cimex 24" planetary machine. The Cimex, like OP machines, delivers a lot of agitation, but does this with a unique 3-headed design. The so-called "deck" turns one way at something like 300 RPM, and the 3 smaller heads turn in the opposite direction at 400 RPM. I use the Orbitec and the Cimex only for cleaning via the encapsulation process.
In reserve I have a steam vapor machine which I may or may not use on tile & grout cleaning jobs.
I sub out wood floor sanding & refinishing, as well as work on marble and similar floors (like limestone).
I use a challenger on residential and on commercial I use a 20 inch dual speed rotary I use a Kirby G7 on all carpeting On stairs I use a Makita 7 inch rotary for cleaning and a Black and decker for vaccuming the stairs.BTW Mark is a big fish in his market. I am just a guppy in a shark tank