Indeed, the Sopranos were much weaker family than the Lupertazzis, this was made clear on numerous occasions. Perhaps they made the NJ mob more powerfull and wealthy than it is in RL, but compared to the NY it was still much weaker. The only reason the Soprano family didn't get "slaughtered" was that the war with NY was a war that only Phil seemed to be interested in. Most of the NY family didn't give a shit about NJ mob/Phil's beef with Tony and many of them probably didn't like Phil in the first place, considering that the family just came out of a "civil war". Nobody profited from this war and that's why Phil was betrayed and ultimately shot. This wasn't a 'victory' for NJ over NY, especially if we consider that they lost 2 key guys. Tony too was probably killed by someone loyal to Phil in that final scene.