I talked about dog bite injuries with an ER doc friend in Louisville- what he saw coming in the ER. In his ER, pit bull and pit mixes caused the most injuries, especially since their jaw strength is so incredibly strong, but chows and chow mixes were known for going for the "kill"- biting people on the neck- literally "going for the jugular", and many times the attacks happen out of the blue- so scary.
Larger breeds, like Mastiffs, Newfs, Rotts, etc. cause very severe injuries due to the dog's mouth and body size and strength vs. their victim. Catastrophic if a 180 lb. dog gets ahold of a 45 pound child.
I see a lot of pit bulls around here on the Panhandle, and a lot of ads to either give them away or sell puppies. This is scary to me! One of my many soapboxes (sorry)- there are certain breeds of dogs that should not be owned by people who don't understand how to train and handle their inherent personality traits, which truly exist no matter what pit bull lovers tell you.
Also, dog attacks are many times concentrated in lower socio-economic areas where certain dog breeds sadly become status symbols, like cars, tennis shoes, etc. We lived in an economically stable area in Louisville, with very low unemployment and very nice housing areas. I worked in a vet clinic, and commented one day on the fact that we only had a handful of "bully" dogs- pits, chows, and rotts in particular. My boss told me that our clientele weren't into those kind of dogs- our patients were more "family" dogs like retrievers, terriers, shepherds, boxers. I will tell you that the worst injuries I ever saw on dogs came from attacks by pit bulls. Awful.
**disclaimer- to all owners of the mentioned breeds- I am just repeating the info told to me by the person treating the injuries****