Would have been more of a proper test if they had used the same fglrx version drivers on Ubuntu and Fedora.
As for Vista, there are known issues with games at the moment.
I would have considered it a great test had they used Windows XP instead of Vista and used the same version of drivers on Fedora and Ubuntu. I know there isn't a whole lot of difference between versions but you need to compare apples to apples on the same kernel base.
It is however, quite interesting anyway.