You couldn't go wrong either way. Spec-wise, they are virtually identical.
They both have USB and headphone ports, no integrated speakers (not a big deal honestly) and both lack G-Sync support, although BenQ XL2730Z does have FreeSync support. Although I can't notice a difference with FreeSync/G-Sync on or off other than in their respective tech demos. In those cases I do notice clearer motion, but in actual real-world gaming, Free/G-Sync doesn't do anything for it.
I would give the ROG PG278Q the edge simply for its on-screen displays that you can turn on. Timers for your MMO games, and a crosshair in the dead-center of your screen for others (won't do shit for Insurgency due to our dead aim mechanic). I personally think it's useless in most games, but when I was using the crossbow in Rust (which lacks a crosshair) I became pretty deadly with it.
For monitors that are virtually identical, it's up to you if $100 is worth the extra HUD displays the ROG offers. I'm also a bit of a Asus fanboy so that would factor into my own equation, but it's probably not a problem for you.
So if I were a Rust gamer, I'd go with ROG... but otherwise the BenQ is the better buy, imo.