Careful of selecting a realtor just based on who sells the most. You're not looking just for volume, otherwise, you would get really high quality products at Walmart...um...okay...so that wasn't very nice to Walmart. High volume could be due to a number of factors, not the least of which could be under pricing properties (sounds odd in these tough times, but does happen).
Since every realtor is going to use the most effective sales tool available, the Multiple Listing Service, you want to find a realtor that clearly differentiates themselves in other marketing tools, and one that has a very good network of communicating with buyers in your specific area. Also, ask your neighbors, and talk with coworkers for references. References are almost always the best source.