The dome is a dome for a reason. It is a 3 dimensional representation of the subject and catches the light falling on, across and around the subject. The dome should point at the camera regardless of the direction of the light source.
The disk, on the other hand, is a representation of a flat surface, such as a picture on the wall. It receives an even illulmination across the surface.
In either case the dome or disk should point to the camera.
I never worked in a studio either.