The Carrera GT sounded like the Diablo in the interior scene (which was in front, so I'm not sure if it shares the sound or not).
The Mazda Vision didn't seem to have transmission whine, not like in GT Sport. I don't think I've seen anyone point this out!
The BAC Mono does have transmission whine, which sounds the same as the previous game.
In terms of thoughts, they sound the same to me as in GT Sport, even the ambient SFX. I don't dislike Sport's sounds though.. at least we're not still stuck with 6's.
Were the tire sounds like GT Sport's? I can't remember.