I didnt see Price is a concern, so get a Mac, they have allways had the best Hardware/Software performance and that OSX kix ..new Macs can dual boot,so if you really NEED windows, you can get the version that you like best after the security patches and fixes and updates are started.
Vista is allready on R1, microsoft says it isnt a patch, but it is a Revision.
You can run any os you want, look at what the os is made for, Macs are for Humans , PCs are crossplatform, Biz or Home Use. After you look at the Vista site, please note all the different versions, Home,Office,Media,School,Server,Laptop, crazy. One Mac OS/X one operating system, when you make something that works, it FUNctions.