Civilization IV Beyond the Sword- just bought both, should I play original or Beyond the sword?

I just purchased the value pack of both games following playing the Civ series for the first time on PS3. I wanted a better experience so I got the Value Pack of Civ IV and Beyond the Sword for my PC. Should I just play Beyond the Sword, or does it contain the original and the only reason I have the original is to have the ability to play Beyond the Sword? Any suggestions????