Quote Originally Posted by Riardon View Post
Performance wise it's never a good idea to play windowed mode. borderless window is still windowed. In full screen mode the gpu is working solely for the game and nothing else avoiding possible stutters. Also some overlays work only in full screen mode. They just have to fix the full screen mode. Window mode is only a temporal solution.
The performance difference is minor. Unless you're running FFXIV on an incredibly weak PC or have encountered a bug with windowed fullscreen, I see no reason not to use it. The purpose of windowed fullscreen is to have the ability to quickly alt-tab, if you're doing that often enough that this bug is an issue, use that option.