Viewfield or reference views. Which to use? Well viewfield is a module where you add CCK filed and you can choose which view you want to have for this field to show. This can be default or can be overridden on node edit form. You can also pass arguments by default or change it on node edit. Reference views is just to change how node reference would look, so basicaly you change display fields. Views reference is another module where you choose a view as field and then enter data for that view and can use PHP to pass argument, problem is this is all in node edit so there is no room for automation or default view and arguments which you would most probably use, so first option would be the best, viewfield.