V-sync forces the GPU to wait for the monitor to be between refreshes before it is allowed to send an image to the display.
G-sync forces the Display to refresh its image when the GPU finishes a new frame.
Since GPU's generate frames at an inconsistent rate, it is a big advantage to have the monitor sync with the GPU's rate of delivery, and not the other way around.
V-sync forces the GPU to wait for the monitor to be between refreshes before it is allowed to send an image to the display.
G-sync forces the Display to refresh its image when the GPU finishes a new frame.
Since GPU's generate frames at an inconsistent rate, it is a big advantage to have the monitor sync with the GPU's rate of delivery, and not the other way around.