Thanks for the input. What if they want to be treated as separate sites? Do you think they should want to be treated like separate sites? The idea is these are franchises all over the country, so they have vastly different audiences/geolocations.

For us, we're really on the fence about which route we should take.

One of my clients has about 40 franchisees who are going to have their own sites on a WordPress multisite installation. The question they're wondering: should these be on subdirectories (thesite.com/this-franchise) or on subdomains (this-franchise.thesite.com)? Which is best for SEO?

Thanks!