Unless I'm confusd about something, if your monitor can't refresh faster than sixty times per second (60 hertz), then it would be impossible for you to notice any difference at a higher FPS. Since VSync makes it so that the game only goes up to however fast your monitor can refresh, in this case 60 times per second, I can't see how disabling VSync would give any real performance boost.
But then, I don't know too much about how VSync works. It may give a very slight performance boost to have it off, even when you're monitor can't show anything more. But then again, disabling VSync can give you graphical glitches, so I tend not to do that.