The person who sells the most may not be the best. As agent who sells new homes can sell 200 in a year all in 1 community so the numbers are skewed. Your best bet is to find someoen who is familiar with your area, familiar with you type of property and someoen who can meet your goals and wished to get the house sold quickly and at the best price obtainable.
You shoudl also ask what their marketing plan, where they advertise, what they think the value of your house is, what they think you should ask and what they think you will get. Make sure they only do assisted showings. Larger agents use unassisted showings where someoen calls a showing desk, usually in a nother state or even country, they are given a lock box code, you have a stranger in your house and no one is there to explain to them what makes your house special, where is the lot lines or how old is the roof. Bigger is not better, often they wont have the tome to give you as they are spread out too much, consider independant brokers, family brokers and such. You will get personal and professional service you may be happier with. good luck in your sale