We have no clue how Yandle would fair on the PK here since AV doesn't allow him to play on it, ever. If you think him not playing on the PK is any indication of how good he would be on it then you are out to lunch.
There is no way Boyle or Girardi are more effective on the PK than Yandle would be. I'd be willing to be a lot on that, especially Boyle.
That being said, I don't think Yandle is better than McDonagh, but it seems that AV's lineup decisions are markedly better when he's out of the lineup. If we didn't have such a dope of a coach, that wouldn't be the case. Unfortunately, the team seems to thrive when Yandle gets more ice time. When McD is out that happens. When he isn't, we often see more Girardi/Staal/Boyle.