If you want GT5 sound vs FM4 sound vs Real life sound for the 787b here you go, there are probably going to be some of the best examples you will find.
http://www.youtube.com/watch?v=81zhOQ5PvaE
http://www.youtube.com/watch?v=rNILs5iPiPg
[Nevermind, can't find a direct feed recording of the FM4 787b, will update]
Must say GT5 is really, REALLY close to the real deal.
Hang on a minute.....you posted up real life...then GT5...but not Forzas???
hmmmmmmmmmmmmm......
here it is.... sorry on this one theres not even a debate....forza smashes..SMASHES GT5 out of the park......like they didnt even turn up....
enjoy.....the sound..
http://www.youtube.com/watch?v=snvabUH0cEs