I could be wrong, but I believe that there's a single engine refresh per frame drawn. So the higher your FPS count is, the less mouse input lag you get (for high FPS players: try capping your FPS at 100 and then 1000 and you'll notice the difference).
However, when your FPS is uncapped, you get screen tearing, and this is probably what your friend is referring to with the "smoothness". With /vsync 1, your display will update at a steady pace (usually 60hz), and with /vsync 0 you don't synchronize with the pace your monitor is trying to force.
However, what you can actually do (which I recommend and have done for ages) is to cap your framerate at a multiple of your monitor's refresh rate, so you get the same amount of visual change with each refresh cycle and there are no "half-frames" being drawn. For anyone saying they or others "hit better" with high FPS, they are wrong. The only difference is simply that your mouse is (much) more responsive with 200fps or more than if you were stuck at 60 fps.
If you're talking about games like Skyrim, Dirt 3 or EuroTruck Simulator (beast game), your friend is right - the smoother the better. But not for FPS games, imo.
EDIT: Also screen tearing is never as bad as Krayce's picture suggests.
However, when your FPS is uncapped, you get screen tearing, and this is probably what your friend is referring to with the "smoothness". With /vsync 1, your display will update at a steady pace (usually 60hz), and with /vsync 0 you don't synchronize with the pace your monitor is trying to force.
However, what you can actually do (which I recommend and have done for ages) is to cap your framerate at a multiple of your monitor's refresh rate, so you get the same amount of visual change with each refresh cycle and there are no "half-frames" being drawn. For anyone saying they or others "hit better" with high FPS, they are wrong. The only difference is simply that your mouse is (much) more responsive with 200fps or more than if you were stuck at 60 fps.
If you're talking about games like Skyrim, Dirt 3 or EuroTruck Simulator (beast game), your friend is right - the smoother the better. But not for FPS games, imo.
EDIT: Also screen tearing is never as bad as Krayce's picture suggests.