Chaos has the good basic stats and survivability of Marines combined with cooler fluff and versatility. There's a Chaos army for anyone's style of play.
Seriously consider them, neither Eldar race are a good beginner's army (just my opinion, let's not start a debate over this)
But asking at this site is a pretty bad idea. Go down to your local gaming store, read the Codexes, compare stuff like fluff, tactics, prices and your enemies (if everyone else there plays Marines, maybe you shouldn't start a Marine army), talk to the staff, and decide.