I once had the opinion that it was just how the dogs are trained. I came across a bull terrier this year that got loose from someone's yard and was running around our green space in Calgary. Being a dog owner myself, I went out to try and leash the dog to get the dog back to it's rightful owner, it was a beautiful dog and seemed to have good temperament. I got close a couple of times but a few rabbits in the area were significant distractions. On my last attempt I just missed capturing the dog and another small dog from a backyard that backs onto the green space started barking, well...this dog took off like a shot, charged the chain link fence, blew underneath the fence and had the smaller dog's (~50lbs) chest in it's jaws. Myself and two other good sized men pinned the bull terrier and had two guys trying to jump on it's jaw trying to get it to release. I could not believe the power those dogs have. It took nearly two minutes and a lot of blood together the dog to release. It was at that point that my opinions changed, with other other sporting dogs you may get a bite and it is bad, but with certain dogs, that have a genetic disposition to hang on at all costs.
You can have statistics on bites, but it is the difference in damage that should be measured. As with most things in life, the way you collect and analyze statistics can usually get you to an outcome that favours the result you desire.
For future reference, (I thought I would never have to use this, but I did), here is a video...and if you think the video is scary, in real life it's way worse.
https://m.youtube.com/watch?v=TnVsm8Rae0k