I'm in the process of a new build, and since it's going to have either 4GB or 8GB of RAM, I'm going to need a 64-bit OS to utilize all of it. I'm a huge XP fan so I'm leaning towards XP x64, but haven't decided anything yet. Since Windows 7 is not an option at the moment, what would be the better choice between XP x64 and Vista x64?