The Yankees do have a clear edge over the Sox in team ERA, 3.80 to 4.17. There are many different stats you can choose to measure a pitching staff. Choose whichever you like. I prefer ERA to WHIP simply because games are decided by runs scored , not the number of baserunners. A baserunner who doesn't score is soon forgotten. I don't have any desire to delve into the more advanced stats involving +,- or x , etc. Keeping it simple, the team who allows fewer runs to score wins the game.