Sour grapes definitely comes to mind. For a competitor to come out with a statement like 'we tested them both and our car was quicker' is the sort of thing every manufacturer says when they develop a new car and compare it to it's rivals.
There is enough evidence to state that the GTR is indeed quicker than the 997 Turbo at least. OK it is a lot heavier and isn't quite as quick in acceleration but it definitely corners quicker than a 997 Turbo and there is one hack of an amount of corners to cover on one lap of the ring.
Now by no means is this an equivalent comparison to a lap of the ring but the recent group test by Autocar in the Isle of Man is probably closer than almost every other comparison test held on a proper race track. Enough chat, here's the video of that day's testing.
http://www.autocar.co.uk/VideosWallp...AR=235168&CT=V
P.S.
I personally believe the new Gallardo will be quicker than the 997 Turbo and quite possibly quicker than the GT2 as well.