Not sure that 'c' and 'd' are really the same. The rotary saws that I have seen (including the Ryobi one I have) seem to be much coarser, much more apropriate for cutting, and built more like a router than the Dremel that I have that seems to be a much finer and multi-purpose tool. I have never seen someone use a rotary saw for polishing and conversely I have never seen a real tradesperson use a dremel to cut drywall (not that it couldn't...)