Well, both games mute the sounds in cockpit view but yes, I agree that GT's version is more muted.
When recording from chase cam, the same conclusions are reached,perhaps even worse for GT. The booming is very pronounced. The 'living room,small and large theatre' modes make a big difference to fidelity as previously mentioned.
The sounds from GT in that particular view(chase) are as you can tell, more meatier, more throatier. More effects are heard. But when higher revs are achieved, they tend to fall off and distort alot...this didn't happen with FM. Roof cam feels sort of 'balanced' if you know what I mean.
Anyway, imo, judging from the recordings, GT's effects sound more 'synthesized,processed' compared to FM which sound more 'natural'.