http://www.uwsp.edu/psych/dog/LA/distano2.htm Check out this link, this particular article was American Bulldog vs German Shepard Dog specifically talking about training and performance of one vs. the other in PP. Upcoming articles will include Sports Dogs vs Street Dogs ... sounds like what we are talking about here. Now I will get to my point... I think there is a difference, not so much in the actual training, sure you can get any dog with aptitude and drive to do just about anything...however I think some will excel more in one catagory than the other. Im not sure what you are getting at here with this being controversial...but I think it is pretty obvious that some "sport" dogs aren't as good at PP and vice versa...when you are talking about a PP dog I think the question is can this dog be beaten? That is to say if pushed to do it's job one will break and another dog may not break. One specific point mentioned in the above link is pain threshold...the opinion of the trainer was that the AB has the potential to be a better PP dog than the GSD for that reason...maybe Im off on a tangent or Im not understanding the question, but Im with the first response I've seen sport dogs that were great at what they did, that I know as a GD/PP trainer and handler I could beat! if for no other reason than size...I could take a bite from 55lb pointer and make him let go (under the right circumstances) a lot sooner than a bite from a 120 lb Rott that is most likely gonna knock you on your ass. One other example I'll give to rap this up... I've seen with my own eyes a handler get mauled by a 140lb Akita...after it was all done and the canine unit showed up, the cop told me his GSD wouldn't have done near the amount damage this dog did, he was just in awe...i In case I'm not being clear let me just say this, there is a difference when talking about PP dogs and the difference is the: All dogs are not created equal...I've seen Jack Russels do protection work! Are you gonna tell me there is no difference between a Jack Russel effectively stopping an Intruder and any 100lb+ dog stopping an intruder...ofcourse not!! I'm talking real world scenarios here.