Why Does Xvids Have Louder Sound Than X264

Guys I wish to ask about audio high quality when enjoying back xvids or x264 information. From what I'm observed xvids have better sound than x264's for instance if I watch a television show that was transformed to x264 I've to show my sound all the best way up might to 45 or 50 but if that very same show was accomplished in xvid I barley have t flip my sound up in any respect it just sounds louder. So I have to ask whats the deal with sound on x264 additionally is that this a codec xvids.life drawback?