WoW is more polished, has far more content, is friendly to newbies, and provides players with several character progression options. Age of Conan is brand new so it has some balance issues and design flaws, but it has potential to be a much better game overall, taking many lessons from previous MMORPGs. Also, the lore is a lot cooler and far less "pulp fantasy" than WoW. It's up to your own personal tastes. I played WoW regularly for 4 years and cancelled my account recently - I haven't looked back since AoC came out.