I'm going to write up an honest comparison between the two games after I get GT5. I'm saving up for it at the moment. My main focus is going to be on the handling physics. I also want to see how "bad" these standard cars are because there aren't many pics of them in the GT5 photo thread.
E92 335i: Space Grey|Coral Red|Aluminum Trim
Hold out for the BRZ STI or... Rocket Bunny FRS.