Power, Temperature and Noise
Nvidia's latest-generation Pascal architecture hasn't yet blown our minds in terms of outright performance, however the architecture's efficiency has to be applauded. GTX 1070 and GTX 980 Ti are similar in terms of in-game framerate, yet the newer GPU consumes far less power.
One of the best reasons to consider a non-reference card is the custom cooler. Asus's triple-fan ROG Strix does an excellent job of keeping core temperature to 61ºC under full load.
And low temperature doesn't mean high noise. The Asus card is silent when idle, and though the fans spin-up to around 1,500rpm when gaming they never become particularly loud.