PS3 or Xbox 360?
PS3 or Xbox 360?
Seeing as it's so specific I think you need to try both and see which you prefer. If it's going to be an all-round device then the PS3 is a better bet as it's more futureproof and has stuff being added to it all the time (of which I have a feeling google TV will be soon as well)
If it's purely about the gaming then potentially the XBox has a better selection, but then you need to try GT5 to see whether that's the game you really want.
Plus Kinect is brilliant fun but I think the accuracy of PS Move may be the better proposition for pure gaming - but I realise both of these are irrelevant if you're only interested in racing games.