For the Windows version of the game, DirectX is used as the graphics API, while OpenGL is used for the Mac version. Though Windows has OpenGL as well, when it comes to the drawing systems for games such as FFXIV, the performance of OpenGL is inferior to that of DirectX.
Yes! Lay the smack down on those hipster nerds who claim Mac is better. LOL Have fun with your overpriced INFERIOR computer. xD