The promise of 4K has been realized over the last few years, with graphics cards growing more powerful while display prices fall. We’ve had 4K monitors, and the ability to drive them at 60fps, for a while now. But that’s as fast a refresh rate as you could get in 4K HDR. If you wanted something faster, you needed to drop the resolution. There are tons of 1440p monitors running at 144Hz, providing fast, smooth, responsive movement at a better-than-HD resolution. In the world of professional gaming, where ultra-fast reflexes require ultra-fast displays, 144Hz is the standard.
Source:: IGN -Reviews