By and large, I'd give the overall edge to the Cartwrights. They're no push-over band leaders, but I think Ben and Vito would hit it off well.
If Sonny could knock off Hoss early, it would tilt the balance of power, but Hoss is much tougher than Bruno Tattaglia.

On the other hand, the Corleones would have no problem with the Douglas men from "My Three Sons." Can you see Fred MacMurray in his ever calm voice saying, "Who put the horse head under the blanket, Chip?"

If you throw in Uncle Charlie though, it's a toss-up.

Now if they were matched against the Munsters...