This is my last reply:
There was some truth in the lag issue (which I said was actually a complicated issue, and it is).
As for the rest, I'm not concerned if you think I'm incorrect. Your both throwing around terms with some truth but your fundamental concept of how VSYNC works is flawed. The entire point is for the computer to generate one frame to be buffered and synched for each frame the monitor draws. Yes, it's SLIGHTLY more complicated then that if you wish to discuss doublebuffering but the above is the basic principle.
The two most important things to keep in mind are this:
#1. Computers will generate as many frames as possible with VSYNC disabled (I had over 300FPS in an old game) and processing on the CPU is almost perfectly proportional to the framerate, thus 60FPS uses about 20% the processing on the CPU and GPU as 300FPS) so the computer runs much cooler in this case with VSYNC enabled.
And it's easy to test with the Task Manager monitoring CPU usage. Go ahead and try a game with VSYNC enabled and disabled (turn down all quality settings to lowest to make the FPS difference higher).
#2. Tearing is a main reason to use VSYNC if you can achieve the required frame rate, such as 60FPS to match the monitor's refresh. It's a simple matter to find games with incredibly annoying screen tearing that are fixed by enabling VSYNC, though tearing varies from almost unnoticeable to unplayable with VSYNC disabled.