Determining the ideal efficiency may sound counterintuitive because aren't we always trying to maximize efficiency? The answer is that oftentimes maximum efficiency is the enemy of the most practical, clear, and straightforward approach. When these two metrics collide, you will need to optimize for both.
Think about getting to the top of a mountain. Rock-climbing the face may be the most "efficient" (shortest) way to the top but the most useful and repeatable way to the top may be hiking the long way.