Each has a slightly different sound, so you can pick a favorite.
It is often said that a large part of what makes a Lamborghini, especially a pre-VW Lamborghini, so fantastic is the spectacle of the thing. The wild looks and the sound of the big V12 models were how Lamborghini managed to make everyone pay attention to their cars, even without the strong motorsports efforts of their competitors. The following video is a great example of this: a Diablo VT Roadster and a Diablo VT 6.0 accelerating down a city street.
Even after all these years, the cars still look insane compared to everything else around them, and still sound absolutely wonderful, but if you had to pick, which has the better sound?