As a former Realtor, I can tell you that many Realtor are selling one thing: themselves. There isn't one company that is "better" than the next, it all has to do with the individual people.
That said, most realtor are selling agents, which means, if you are BUYING a house and you go to the listing agent on the house you are interested in, they are required, by law, to represent the seller, not you. They can't tell you anything about the house that might hurt the seller, just like a lawyer can't betray confidences of their clients, no matter how bad the information might be.
If you are thinking of selling a house, go to your local Realtor Association and ask which Real Estate Agent has sold the most houses the past year (if they will tell you), and ask around for peoples' opinions. If you are buying a house, ask every person you can who is a good, honest, hardworking agent and then ask that agent to enter into a Buyer's Agent Agreement that you both sign. That way, your agent represents YOU and your best interests.
That's the biggest thing I learned about Real Estate during my short career: Only the seller is represented by ever Realtor unless you specifically enter into a Buyer's Agreement.