Scott is right. If you are a home buyer, a Realtor is worth it. They shouldn't be charging a buyer anything, and then you have the best services available... services that put these other websites to shame.
I'd stay away from both if I were you. Find a great REALTOR that will get you foreclosures and REOs. I put all of my clients that want these properties on an auto-notification list. As soon as the property hits the market, the same day, same hour, they get an email and I get the same cc'd to me. If they like it, we go see it. If it's something they want, we buy it. It's a pretty simple process.
Forget RealtyTrac, just click on the Find a Pro at the top of this page, put in your city and you'll find lots of quality, experienced agents.
Scott Miller, Realty Associates, Boca Raton, FL
Most of the time, realty trac's information is very outdated. I sometimes get calls about properties that have sold months ago. Find a realtor in your area who can send you an automated list of properties that fits your criteria. Realtors love this option because it requires no additional work on their part. Or, you can use trulia to find properties. Both good options.
Best of luck to you.