I think his issue is that most TVs are 30hz, 45hz, or 59hz. Unless he has a high end TV that's running 120hz, but those are rarely purchased because of their price. Vsync essentially caps FPS at the display's refresh rate to keep the screen from tearing(looks like horizontal lines if you move really fast), through a method of delaying some frame renders.
So if he has a 30hz display that could result in a 25fps performance. Definitely worth a try to turn V-sync off. But you can get some screen tearing but it's no big deal unless you're one of the few people that it really bothers.