Commercial or - dare I say - residential? Or both?
Commercial:
Go with 175, Cimex or OP. The variables will be frequency and type of work and how often you plan on extracting. For affordability the 175 can't be beat. For efficiency and ease of use it's the Cimex (especially if you plan on flushing from time to time). If you want to encap and pad cap and do so easily, then look at a wheels down OP.
Residential:
Go with a 175 or OP along with a
CRB. No matter what anyone says, the
CRB is a must have for residential VLM. Vacuuming alone simply cannot remove what a
CRB can from residential pile. The machine you choose to go with your
CRB will based more on convenience and preference, though I would lean more towards a wheels down OP. It's easier to use and arguably cleans better as well.