Saying you should go with an agent for a single factor, like "they have more deals closed" is ridiculous. Ultimately, that says every person is the same and has the same needs and expectations.
Should everyone buy a Hyundai because they are the most sold car today?? Do you drive a Hyundai?
Should everyone buy in 89131 because it's one of the most sold zip codes? Do you live in 89131?
I agree with almost everyone in this post; it's a variety of factors that connect clients and real estate professionals. It's the social connection, the friend's positive experience, the agent's portfolio, the agent's spoken languages, the agent's experience and specialty (e.g., Sue Tonic focuses on short sales, and will close more short sales than me or you), the exposure the agent provides to certain targeted markets, the agent's resources, the agent's adaptation to new technologies, and much more.
There's no one factor that is right or wrong, everyone is different, and everyone connects on different levels and factors.
And, we live in a free market so that we can choose what we want, not what we're told; we can make our own decisions based on our own criteria.