Frankly nowadays if you are looking at 144hz gaming regardless of resolution, I'd throw in my lot with nvidia. Unless you intend to find two or three r9 fury x's to crossfire and somehow have the space for three 120mm rads, I'd go without a freesync monitor. Not to mention that most local service providers will have a decent warranty time regardless of monitor, though it might be the largest deciding factor-do note that if it is the only monitor in your system that you will be down and out for the count if you do decide to rma either product. That said, online reviews of the product and more research done by yourself would propably help regardless of my or anyone else's words on this forum.
Then again since it is I that is giving the advise or contributing to the discussion, I would wholeheartedly reccomend the Asus. If you find a cheap deal for it on Amazon or Newegg (any less then 600usd) then go for it, otherwise the PG279Q at ~780usd is more worth the money. At 1440p 165Hz the 27 inch monitor justifies its price premium by virtue of the specs said previously, instead of being TN and 144hz which can be found on many cheaper monitors, including Asus' own VG248QE at 230usd on Amazon. Paying double the money for gsync? Frankly it's ridiculous, as for 460 you could have bought two displays in the place of the single PG248Q. But if you have enough recources to purchase the PG279Q I sincerely implore you to make that buy-a GTX1070 would be adequate to drive the display, but something closer to the 1080 would be more ideal as 1440p >120hz is not an easy task regardless of the game. I hope this finds you in good health and proves somewhat of a help!