Potential score = highest score you could have had if you had started all of the right players at each position. Survivor leagues that are common now where you draft or pick a big team and do nothing else for the year (such as the footballguys.com contest) use "potential score" as your actual score for the week.
Bench points simply takes into account all of your bench players, even if several of them were of the same position and you couldn't have started them all. We picked potential score as our first tie-breaker for the playoffs, with bench points second, as we thought potential score reflected how well your overall team was, or could have been, a little better and should be the first choice.
Regardless, for the original post, if there isn't a rule in place for tie breaking, it should be a tie. Or a new week, I still think a Week 17 tie-breaker is the best idea.