MusicRadar guitar editor Chris Vinnecombe used Audacity (a music editing program) to analyze Metallica’s Death Magnetic, and the results are (moderately) revealing: the audio is better on the Guitar Hero version of the album than on the CD due to over compression. Basically, if you want your copy to have dynamic range, stay away from anything that you can’t use a plastic guitar to play along.

I’m not going to pretend like I can adequately explain this, so go over to Wired to read the whole story.