As others have said, eBay has much wider exposure. But their fees, and packing and shipping a bike is (to me) a major hassle. You also risk the person saying it wasnt described properly and wanting their money back.
On the other hand, CL buyers expect to pay pennies for everything, so getting a decent price is pretty tough, imo. Personally I try to be careful what I buy, so that I dont have to sell a bike later, because it's a pain no matter which route you go.