I have this monitor and I have also used the Asus and BenQ equivalents, but I have an Nvidia card so I don't use Gsync. You get what you pay for. The black contrast leaves something to be desired and the colors are pretty washed out, but it does the job. I'm not going to say it's a bad monitor, because it isn't, but the panels on the BenQ and Asus are better at color reproduction and contrast. At the end of the day though, it's still 144hz (you can even OC it to 165) and the response time is excellent. I'd say get the BenQ if you're a VERY competitive CSGO player, the ASUS if you're more of a casual player, and the AOC if you're more of a casual player and want to save a few bucks.
EDIT: Also for some reason the backlight on the AOC is really bright and can't be turned down to an acceptable night time level, I have it on 0 brightness all the time. Freesync doesn't matter for 144hz btw, if you're above 60fps then all it does is increase latency.