I like all of them really, the 911 sound great, apart from in WEC where for some reason they have muted all the GT cars.
The Bentley was great live, as was the M6, the old M3 coupe was the best sounding overall.
But my fave would have to be the Gallardo, mainly because I had a great setup for it at Monza and ACC and won loads of races in it, and nobody ever expected you to win in it.
Big shout out too to the GTR Nissan.