the Dolly is most like a proper camera. think of it like a camera on a tripod. while the main, aux, face etc are locked to a specfic idea. (Main on the scene center, face on the face etc), the Dolly is the one that you can pick up, move and point anywhere you want.. just like in real life. personally it's my favorite one because of it's flexibilty and it's fine control ... :)