Overall, the novel makes a clear distinction between city and country life
This distinction is also reflected in the way each locale affects crime-solving. The city's advantages involve the networks and directories which Holmes systematically uses to catch criminals. For example, he is easily able to track down the cab driver who was driving the bearded man.
However, Holmes moves the investigation to the moor precisely because there are fewer people, and less suspicions of wrongdoing. Because most people there accept the hound legend as somewhat true, he can more easily observe their behaviors and narrow down his suspects. However, country networks are informal, and hence more difficult to explore. For instance, Watson only finds Laura Lyons because Barrymore helps him.