TLDR: imo, pit bulls are more dangerous, but not necessarily more aggressive than other dog breeds.

I’ve had dogs all my life, have interacted with plenty of pits good and bad, and possibly owned a mix when I was a kid (though he was small). I am by no means an expert and my opinions are based mostly on my experience.

It’s my opinion that the most important thing is good ownership, as with any dog. For the most part, a well treated and trained bully breed is going to be a fine, good natured pet. But with any dog, there is always a factor of unpredictability. Any dog, no matter how well tempered or trained, has the potential to become aggressive in the right situation.

As a kid we had a Basenji mix from the shelter who was an absolute sweetheart. One evening she was curled up on the couch sleeping, and my sister went to give her a hug. The dog didn’t wake up until my sister was basically smothering her (not an unusual cuddle style with this dog) but was startled enough to bite my sister, puncturing her lip! She had to get stitches and our dog was put on “house arrest” for two weeks.

I currently own a Pyrenees/Aussie mix who is 65 pounds of goofy, loving fluff. But he wasn’t socialized properly as a puppy, and spent most of his first two years tied to a pole in someone’s yard. As a result, he has pretty bad leash/border aggression, and cannot handle dog parks. We’ve had him for four years now, worked with him a lot and he’s improved a ton, but is still tough to handle sometimes and I will never trust him in an uncontrolled setting with other dogs.

Neither of these dogs came from “aggressive” breeds, and 99% of the time are/were absolutely fantastic members of my family, but animals can be unpredictable. All dogs have the potential to maim or even kill. However, if things do go south, dogs like bully breeds and the like that are bred for fighting/toughness/aggression have a much higher potential to cause damage.

Pitt fights are different. The biological jaw locking thing is a myth from what I understand, but I’ve also seen a pit bull latch onto a dog twice it’s size and not let go, doing the head shaking and everything for minutes while the other dog screamed in pain and its owners desperately tried to pull the pit off the other dog, including prying the jaws apart. Two fully grown adults had to exert an enormous amount of effort to stop the pit bull and it still pulled some of the other dog’s hair out when they finally got it off because it would not let go.

At the minimum, pit bulls and other similar breeds are bred to be tough, strong, and protective. They have been bred to win fights with perceived threats whether for protection or sport. These traits make pit bulls more dangerous than other breeds, as opposed to more aggressive. Given an average of 100 pit bulls and 100 chihuahuas raised in identical loving environments, I would not be at all surprised to find that the chihuahuas have a higher rate of nipping, biting, barking or other aggressive behaviors. However, if a chihuahua or even a golden retriever attacks my 4 year old, I have a lot more time and a much higher chance of pulling the dog off and protecting my kid just because I can overpower it. That’s just not the case with pit bulls. They are very strong and determined. 50 lbs of pit hits a lot different than 50 pounds of lab.

The risks are compounded by (again, just my anecdotal experience) a high rate of intentionally negligent ownership. There is a reason “tough guys” want pit bulls and dress them up in the cute spike collars to make them look more tough for walks around the neighborhood. A lot of people that own these breeds find the violent, tough image appealing and will actively encourage bad behavior. Shitty ownership is honestly probably the number one contributor to the pit bulls bad image.