The Best Person
Who do you pick to run the community?
We usually advise against the intern. They simply don't know what it takes to develop relationships between members. The problem is the intern is often the best available choice. Note: available.
Given a choice between an intern who will commit their entire time to building a community or an experienced marketer who will spend half their time on the community, pick the intern.
You want someone that can focus their full efforts to cultivating an online community. Very few professionals can handle the change. It's hard to be planning a PR campaign for half a day then dive in and start chatting to members. The nature of engaging in thousands of micro-interactions a week is contrary to every habit many have learnt over the years.
If you don't have someone that can dedicate their full time to building a community, hire an intern that can.