The disc system allows you to add the pages that you want and to have more flexibility in customizing your planner.  If you want a smaller, more portable planner similar to the spiral quarters, you can just have a single quarter with 3/4' discs in your binder.  Or, you can use larger discs and add the journal, or perhaps you want to carry the full year with you.  With the disc system, you can punch your own pages with a hole punch made for the disc system (sold at office supply stores), and add the extra pages you desire. (Discs sold separately)