This is a tough question...mostly because it really all depends on the dog. There are dogs that will protect/bite a true threat without any training, there are dogs that won't bite any human due to training (most pets are taught not to put their mouth on humans), there are dogs that will engage a sleeve or a tug but won't engage a human, there are dogs that will run away and hide, there are dogs that will bark and make a big fuss but really not bite, there are dogs that will bite out of fear when cornered, and there is everything in between.
The biggest difference between a "personal protection" dog and a Schutzhund dog is more than likely the amount of pressure the PP dog has had put on it during training in order to withstand a true attack and a threat that might fight back. A Schutzhund dog doesn't get tested to the same level of pressure that a PP dog SHOULD get tested to. I know someone with two HOT IPO3 dogs and on IPO2. She said that one of the IPO3 dogs would probably be able to withstand the decoy/threat fighting back, the IPO2 dog probably would as well, but the other IPO3 dog probably wouldn't withstand any type of large pushback from the threat. But none of these dogs have ever been trained or tested in a situation where the decoy/helper would actually fight back and try to get the dog off.
This answer really depends on your trainer, your dog, and what you want. No one can answer your question as to how an IPO dog would react because 99% of IPO dogs have never been tested in a real life situation. It's also extremely difficult IMO to replicate every single possible scenario the dog might encounter in training and that's why most people will tell you that a PP dog is born and not made. A dog with solid nerves, a dog that isn't scared of anything at all, a "natural."
Does working a dog in IPO give you a better idea that your dog is more likely to defend you than a dog that isn't trained in IPO? Probably...but that might also have something to do with the fact that the majority of people that don't train in IPO don't play tug the same way, don't allow their dogs to ever put their mouth on a human, and tend to correct any kind of aggressive or guarding behavior in their dogs.
I think you really have to understand the commitment it takes, and understand what you're expecting out of your dog. In my opinion, IPO gives you goals, gives you benchmarks to reach, and will give you the satisfaction of accomplishing something. Training just a PP dog...you really have to make your own goals, and as someone (I'm assuming) that hasn't done bite sport of any sort, you're not going to be very good at seeing the week to week progression of your dogs biting and reaction to pressure. I'm assuming this because I'm in the same shoes you are and its extremely hard to notice the small improvements a dog makes week over week. You also need to really trust your trainer and trust that they know what they're doing because YOU have no idea what is right or wrong at this point.
Be very careful, if you trust your helper/decoy then you can believe them, but also remember that at some level they do make money the more times you come and the longer you're training.
Last edited by martemchik; 01-18-2014 at 02:07 PM.