Getting a 13-in rMBP for Christmas (2.6/512/16) and will want to install a Windows VM (no bootcamp) for the occasional Windows app. I'll be using VMWare Fusion Pro 6. I have access to both Windows 7 or Windows 8.1 and have no preference between the two for this purpose. (My other daily systems use 8.1). Do either of these behave better than the other in a Fusion 6 environment? I'm hoping to use Unity mode, if that makes a difference.