I started both groups late last year when communities rolled out. They are both moderated so I can try to keep out spammers and sales pitch happy vendors. So someone has to apply for entrance before getting in to both. This group was meant to be open to B&Bs and related vendors/industries. So if White Stone Marketing wanted to apply in for example, as long as they read and would abide by the rules I would let them in. I have booted several vendors and couple of B&Bs already for pitching sadly. The private one was meant to be B&Bs only.
The only difference being one (this one) is public, which means you don't have to be a member to see the content. The other is private, so you have to be allowed entrance to see the content. (Google sees it I am assuming though, Big brother sees all) but it's not searchable to the general public. Did that clarify?