I would actually recommend both monitors! The Overlord X270OC is the perfect gaming monitor for any game and is capable of up to 120Hz. To achieve the higher clock, no special tools are required any longer. The refresh rates can be created using the Nvidia control panel or ATI Control Center interface. I use my X270OC to play both RTS and FPS games and have never had an issue using the higher overclock frequencies. On the other hand, the Asus monitor is for those FPS 'twitch' gamers that are more competitive and need every extra smidgen of advantage that a low response, high refresh rate 6-bit TN panel has to offer. Also, the Asus monitor will have the much coveted G-Sync technology that is awesome! I know because I own the Asus VG248QE G-Sync monitor (also purchased through Overlord) and love it! It really is a game changer in FPS games.
Ultimately, the choice is up to you and should be based on what kinds of games you play. Performance crown goes to the Asus G-Sync monitors, but the beauty crown goes to the Overlord H-IPS 8-bit panel for a superior color gamut and contrast ratio.
I wish you luck with your decision!