Natural protectiveness you only need for property guarding. For a PP dog you need: a social dog that isnt too sharp, strong nerves, good balance between prey, defense and fight drives, plus trainability. Environmental stability is very important too. These traits arent breed specific, rather individual specific. But, with some breeds you have better chances of finding the right individual than in others. It all comes with selection tests the breeders put their stock through. Out of the dogs you mentioned : a well bred AB or Presa would be the safest bet. If you really need a top worker, look at working line GSDs, malinois, dutch shepherds, rotties, bouviers. The first three the ratio of QUALITY/QUANTITY is fairly easy to find. The last two, are not so easy, but they are around and can be SUPER animals. As I've said: its not the breed, its the dog in front of you.