Capital Advisory/Placement Question

Hey guys - maybe I am missing something, but this week I was trying to figure something out regarding real estate PE/capital market groups.

To provide some context and focus, we are specifically talking about providing the service of identifying equity capital sources, ultimately resulting in the investment/placement of said equity into a deal or fund. I noticed that these "groups" fall into two categories, non-registered and registered.

Non-registered examples include: Ackman-ZIff, Carlton Group, C&W et al. Registered: Eastdil Secured (through Wells), Park Hill Group, HFF (through HFF Securities)

So what's the difference? I presume the non-reg'd groups are only offering the service of introducing PE JV partners where the fee becomes a finder's fee, whereas the registered placement agents can solicit from passive investors such as LPs for the purpose of investing into a fund, along with any other kind of solicitation or placement of equity.