I had a Hazro that I had to send back after a period of time because of build issues.
This is all going to be really subjective but for me, 120hz in gaming has made a big difference.
When I had the Hazro and ASUS side by side I did a few tests (nothing scientific, only by my eye) where I would look around an area in a game, moving the mouse at varying speeds.
All of the objects and scenery in 120hz stayed absolutely crystal clear and solid no matter what speed I moved the mouse at while on the Hazro, while it did look marvellous, I did notice some blurring and it did feel more sluggish (for want of a better word). It's hard to explain but the 120hz feels more responsive in real world gaming terms.
It is all subjective though. I'm sure just as many people will prefer the 1440 over 120hz as not.