Closer Endurance Ratings

I have recently come to appreciate the importance of drafting a Closer with an endurance rating of at least 3 so that he can get 3 outs in the 9th. Could someone tell me the benefit of a closer with an endurance rating of 6 vs 3?

He can come in at the top of the 8th and close for 6 outs without fatigue if runners don't get on base. Same as 3 just can go 6 outs.