"Forza 4′s cars will boast a polygon count of over 1 million compared to 400,000 in Forza 3"
"The high poly count makes sense given that you can open every body panel via Kinect, though how this translates in-game remains to be seen."
"GT5 has 200 premium models with 500,00 polygons along with a further 800 cars downgraded to 100,000 polygons. Forza Motorsport 4′s entire roster of over 500 cars will potentially have twice the amount detail of GT5′s Premium models at over a million polygons."
- so my thoughts are if you are going to dare go that highpoly, you better knock it out of the park and have interior, maybe even engine etc for showroom purposes, im not sure what count the in game models are