The sound is much better, but not the reason to buy one. You can hear my car on the dyno with it here....

http://www.youtube.com/watch?v=EqoD0...e=channel_page

It took a half second off my 1/4 mile times, as well as many others here.

Personally, I also like the idea of being able to see my engine, not a giant hunk of plastic, but that's all personal preference.