Create a Multisite with sites to sell: should it be subdomain based or subfolders based?

Hi. I am willing to create a multisite to host different sites that I’d sell to different clients. I’d Use the Domain Mapping plugin to “mask” the multisite URL’s with the client’s domain URL. I have read that there is some difference in terms of SEO between a subpath based MS and a subdomain based one; as the subpath’s option brings benefit to every site on the network… I’d like to know which option is most recommended to a business like this; having into account that clients would have nothing to do between them; and might even be competitors.

Which option would you choose in this case?