The question is wrong actually. You should not start by asking which technical implementation you use, but what staff structure you have on your board, and then assign people the tools they need to do their job within the staff group. Always give people the minimum of tools/permissions they need to do their job.

Marco is right (Damn, that hurt to say! ;)). Giving too much power can sometimes lead to accidents (deleted threads, users, etc.) as well as swelled egos, which in turn can cause friction and problems later on down the road. Trust is a very important factor, also.