I was in a similar situation last month. I was going to get the Viewsonic just because I have had good luck with their brand in the past. My brother has the Acer and it DOES look very nice (his did not have any of the issue which these monitors can sometimes have). In the end, I just could not decide and with CES coming up next month, I didn't want to buy then regret. I got a deal on a 24" ROG which will tide me over until I see what 2017 brings.
One thing with the Viewsonic, the USB ports are on the right. That would bother me since I am right handed and that is where my mouse cable is. May not be an issue for others.
The three IPS 27 inch gsync monitors are all using the same panel. (Or is it four, did AOC ever release theirs?) They're all an AUO brand AHVA panel and a gsync module from Nvidia. The differences come down to the onscreen menus and the plastic surrounds. They have pretty much the same feature set, they all have the same defects and panel lottery.
My choice, the one that is cheapest when you're ready to buy.