Fidelity overall has MUCH better performance. See for yourself. I'm a financial analyst. Not to sound like I know everything, but I do this for a living. Vanguard does a great job of marketing themselves as the dirt cheap alternative. Both Fidelity and Vanguard are cheap.
Cheap is not everything. It's worth paying a few nickels for better performance over the long run. Fidelity has much better research, performance, and a great website. Not to mention, Fidelity customer service is outstanding. From personal experiences, I know that their back office is fully licensed, so they can talk shop with you.
I've used both. Fidelity is better.
Side note: You can buy Vanguard funds through Fidelity.
