Well Overwatch is an odd ball as well because the game simulation time is directly tied to FPS as well which is dumb. So yeah you want the highest FPS possible in it. Battlenonsense also covered that here: https://youtu.be/nilBzupE4Cc
From all the graphs and explanations of Overwatch, it seems like a poor game to test this stuff in right?
Either way, I think generally speaking, except for a few fringe/minuscule cases, you WANT Gsync.
Personally, I don't believe you should buy Nvidia if you can't afford Gsync. Doesn't even make sense to me, again barring a few niche situations.