Hello John,
Your question is basically "what is the best bite or teeth matching configuration a catch dog should have?" This is strictly MY OPINION concerning dogs teeth. I feel that a dogs teeth should match up even as possible. I don't like an overbite and don't like an underbite. When ever i raise a dog or buy a dog or have one given to me, I don't take one unless they have matching teeth. I also personally think a catch dog can hold better when he has matching teeth. Now, with all that said, I personally know people that have dogs and especially catch dogs that have both an overbite and others a underbite that catch real well and their owners love them. But thats not what I want in a dog. Pretty much in all registries of breeds except for maybe the English bull dog, a dog is culled for having an over or underbite. But the majority of folks that hunt hogs don't have registered dogs, but I still prefer a matching set of teeth in a dog. In regards to American bull dogs having underbites--I've owned several over the years, and none have had underbites.
Good luck with your dogs,
Jim