vagrant-windows is not working at all on OS X at the moment.
https://github.com/WinRb/vagrant-windows/issues/177
Near as I can tell the issue has to do with the WinRM gem, which I'd debug myself, but looking at the source and what it does, I am woefully unequipped to debug that issue without spending a lot of time that I should be spending on other work. I'm simply too far removed from the Windows world to even know where to begin.
VirtualBox can be godawful at times. What's not working for you?