Interesting stuff. Obviously, getting the proper volume of work is critical to growth. 3 sets can be fine depending upon what your goals are for that day, such as budgeting your gym time to train multiple bodyparts. How often you plan on training the bodypart in the week can also be a significant in determining set totals for each session. Addressing another discussion point, muscular conditioning certainly plays a role in determining how well you are going to respond to what one would call "medium effort sets". If one is already well conditioned, one will need to work closer to his or her PRs (5RM, 10RM, etc.) in order to advance muscular conditioning. Which means medium effort sets on a consistent basis will not work for the advanced athlete and will lead to deconditioning.