The thing I like about Southland is that it covers the small barely-notable moments too. Most cop shows focus entirely on a central plot. A guy gets killed, and everyone on the show is working on solving it. Southland does have the detectives doing just that, but it also strays and covers completely random things like having the beat cops catch a guy taking upskirt shots in a mall. They confiscate the camera and never mention it again.
I also like that people actually do their assigned jobs. Unlike, say, CSI where forensics people are doing interrogations, etc.. the detectives investigate, the police handle the scene and patrol, and so on.