Their mentality is about making money, and avoiding murders whenever possible.
Prop. Joe tends to be the stand-in for the Eastside in general, and it’s reflected in him the most. I don’t remember Joe ever being responsible for killing anyone else throughout the entire show. He works with Stringer to get access to the high-rises, helps form the Co-Op, refuses to go after Mouzone when he shoots Cheese, backs down from Marlo and Omar. He’s all about, “buy for a dollar, sell for two, later for all the gangster bullshyt”.
On the one hand, it tends to keep the police off their backs. The Barksdales and Marlo become targets for the BPD because of the all the bodies they drop. But the only time you ever see McNulty and co. ever express any interest in Joe is when they’re trying to use him to get to Stringer.
But on the other hand, it definitely makes them softer than Westside guys like Avon and Marlo. Which is why they turn to Marlo in the first place to get rid of the NY dealers, why Joe introduces Marlo to the Greeks to avoid a fight with him, and why none of the other Eastside kingpins do a damn thing when Marlo disbands the Co-Op and declares himself king of the Baltimore underworld.
At least, that’s my reading of it.