Answer:
That depends on a lot of things. If you get somebody who only started with computers very recently and give them a Linux machine... It wont be long until they get very bored and frustrated. So Windows Vista probably would have had the advantage there.
It also depends on what you want to do with the machine aswell. If you plan on playing all the latest games. Then again, windows has the upper hand.
Though if you have a crappy computer and want to get the most from it, then installing windows vista is the last thing you want to do.
I have found over the years, if a particular customer keeps comming back to me with virus after virus I simply put Linux on their machine. Problem solved.
Vista (along with any MS OS) in my opinion is for people who dont want to know anything about computers. Its there, its completely dumbed down (even think of windows server 2003 - everything you do is through a wizard), its already preconfigured so when you get it you dont to have to start worrying about configurations that have to be made before you can begin. Take Linux gentoo for example, when you get that - you know its going to be about a week before you get it up and running, get all the programs on it that you want, get the security tweaked etc... But in the end the gentoo machine will be way better than the Vista machine.
With Linux, you make it suit you - but it takes work. With MS its ready to go, but MS have to make it so everybody will be happy (but as we all know, you will never keep everybody happy).