Both are very formidable and great protectors. They are similar in a lot of ways. As far as a guardian, I would give a slight edge to the Boerboel. The Presa's prey drive is very high, they want to go after the threat. Boerboels, more than Presa's will stay by you and guard you against a threat. Both are great protectors and will put their lives on the line to protect their owners.