I have considered Zenbook over my MacBook Air but I have not changed yet. I am somewhat reluctant moving back to Windows but in the same time I am not much of a Apple fan either. I guess I am on deadlock here, waiting a linux miracle. So, it all boils to software.
But you can run both on the Mac, at the same time too. I do a lot of OpenFrameworks stuff for in-store retailing (touch screen, interactive displays) and I can run opengl openframework apps in Parallels 8 at 60 fps no problem in coherence mode (WIndows apps run in windows integrated with your mac desktop). They aren't exactly trivial apps either (some run at 2560x1440 and are doing Kinect processing + OpenCV + 3D). I develop with XCode, flip over to Visual Studio to recompile and debug (we dev on macs, deploy on Windows).
