Personally, I think wins vs SOS should be all the matters. It may not be the best prediction but I think the point of sports is to win the game. Taken to the extreme, should the 4 teams that go to the Final 4 be the teams that won their games or the teams with the best performance metric through the first 4 rounds of the tournament? The RPI can be improved but I still believe the system should be based on earning your way in by winning games, not by having better offensive/defensive efficiencies, point differentials, etc.