If I know the customer really REALLY wants the safest product I have, I will use either of the 2 Bioforce products: labelled as "Carpet & Upholstery Cleaner" and "Outsolv".
I know from discussions with the company owner/president (Glen Nelson) that these are 100% vegetable product. If the customer is primarily interested in using a "green" product, I am more likely to use Vacaway's encap product, which contains a trace amount of a polymer - a synthetic material - in order to have it behave as an encapsulation product.

Mark, which one is the better product for cleaning or is there really not much difference?

I cannot see any difference. With an OP machine, you have such a high level of agitation, I believe most of the work is done by the scrubbing action, regardless of the quality of the cleaning product.