Currently the best monitor for gaming is the Asus ROG Swift 144mz 1 ms monitor with G-sync but it is very expensive due to the 1440p resolution and the g-sync.
Personally i don't like the idea of buying a 27inch for only 1080p resolution, however if you are fine with that you have to ask, do you want the better colour that pop and better viewing angles of an IPS monitor, or are you wanting to sacrifice a little of that for faster mhz and refresh which is better for gaming. This is an example of a 27 gaming monitor that isn't 800+ dollars.
http://www.asus.com/ca-en/Monitors_Projectors/VG278HE/