Vsync is there to fix the graphics from "breaking up" or showing "tearing" for certain cards. In no way they reduce the CPU available for the simulation engine.
For gaming PCs with reasonable power In any case, Vsync will maintain the display frame rate to 60fps without huting the smoothness of the game, while making sure that the display is free of "out of sync artifacts".
So if you get Zillion of FPS without Vsync on and you have no visual artifacts, you can leave it at that. If you do experience some visual artifacts, turn Vsync on and you will NOT hurt the rest of the sim performance, despite the fact that the FPS are pegged now at 60fps. Anything over 25FPS is smooth enough for the human eye and considering that the PC already has enough horse-power, you will have a smoothly-running, clean display sim.
/Admin