I'm not a huge fan of overly loud pipes. By the time they sound loud to the operator, the bike is hella illegal on the noise levels, and that makes non-riders pissed. There's talk in the US about banning bikes in national parks for instance because mostly the potato-potato dudes (but certainly also ****** rocketeers) ride with essentially straight pipes, to the point where it is messing with the wildlife.
There's a comfortable growl and then there's just antisocial. I really wouldn't mess with it, personally, but that's just me.