Honestly I can't tell. That's how good GT5 graphics are.
The Audi Le Mans Quattro for me :) Only several more hours 'til release
Gran Turismo 5 will be a great experience for me as I'm new to sim racing, but not so much as I did play forza (the first one) before. So kinda have an idea of how it will be presented
1, 5, and 6 are GT5 *look at top right corner*