Considered at face value, the Drunken Clam doesn't seem to stand out over Paddy's, Cheers, or really any of the other choices. Each of them feels like a great time; who wouldn't want to drink wine in a soda can with the Gang?
Or lay down the law with Dalton?
Each of these haunts has its fair share of interesting characters, cool guys, and skells. You could probably write a "I Love This Bar" song about each of these. But what sets the Clam apart isn't hanging with Peter, Quagmire, Joe, and Cleveland, fun as that may be. What sets it apart is the ability to make a completely random cultural or historical reference and have it come to life.
Part of the fun with these hypotheticals is applying the conditions of each bar and the parameters of that reality to yourself and wondering how you might like it. So within the world of Family Guy, I'm going to go ahead and assume that if I hung out at the Clam, I could make allusions and references to random stuff and it could be instantly visualized by me and all my buddies downing cold ones. It would be kind of like my real life, but the references would be funny or relevant.
That, and drinking a dirty martini with a talking dog would be awesome.