I don't think "Metal is already faster than OpenGL" tells the whole story, guys. Maybe it would be more accurate to say "Metal is already faster than Apple's OpenGL". In other words, how does the same test perform under OpenGL in OSX and OpenGL in windows ?
It might still be faster or not, but OpenGL in windows might perform better than it's older cousin on OS X side, because of better drivers and/or higher OpenGL version. Ideally, the latest manufacturer's drivers should be used on Windows (e.g. nVidia or AMD) and not Apple's.