I would argue that the IPS "gaming" panels incorporating G-sync are pretty poor IPS quality panels (other than speed-related performance). Yeah, you'll get the viewing angles and color accuracy associated with IPS, but the backlight bleed is atrocious. I wish I would have kept my PG278Q (TN). It was better than my PG279Q or the XB271HU I had and returned after a day.
I still run with the PG279Q, but it definitely wasn't worth the IPS premium. If I hadn't sold my PG278Q just before picking up the XB271HU (could stand this for about a day) and subsequently the PG279Q (also not good but not as bad as the Acer), I would have also returned my PG279Q.
What good is color accuracy if the bottom right and top right corners of the screen (bottom right is especially terrible on both the Acer and the Asus IPS) in dark scenes are washed out with the backlight bleed?
What good are mega viewing angles if you're sitting directly in front of the panel? Maybe so your friend can watch the same thing your looking at while sitting to your left or right? The backlight bleed also makes the viewing angles a moot point for darker scenes.
I think Acer and Asus produce poor excuses for 27" IPS gaming monitors (although the Asus PB278Q non-gaming monitor I use for work is fantastic).
That being said, I'd prioritize my monitor selection as such with a GTX 1080:
1) G-sync - Greatest thing since sliced bread.
2) 1440p - Best res to use with a GTX 1080 to stay well above the 60 fps mark with just about every title (most around 120fps).
3) 120Hz+ - Helps with the smoothness of the image.
4) Good contrast. This helps with discerning details in darker scenes.
I really don't think the panels they use with the Asus and Acer 27" IPS gaming monitors are worth the IPS premium since they are of a lesser quality than those IPS panels historically known for the color accuracy and viewing angles.
Do you want top of the line TN or low-end IPS? If I could go back, I would have stuck with a top of the line TN.