Pitbulls lead in fatalities as they're strong, have very powerful bites, have very high pain threshholds, and often don't give warning of an attack. Unfortunately the worst kind of trash breeds and trains the dogs to be aggresive, even though they can be very good dogs around people. I had a 70lb pit bull, selected as the last of a litter of 13 hoping that any agrresive dogs had been previously selected. It worked well as he was a worthless guard dog regarding people, friends could walk in the house without knocking and he'd want to be petted, he'd play with neighbor dogs when either got thru the fence, but he displayed attack postures if other dogs ventured into the front yard until the other dog was introduced. A pending attack was subtle as he'd just start drop a bit and start a funny walk towards the dog, no growling, no bared teeth, no hair standing up. I'd pull the leash, introduce him, and all was fine as they'd start playing.
They don't bark much, ours didn't really bark until the ex taught him to, have short hair, and heal very fast so vet bills are very low. They're loyal, are fun to play with, and make good companions. The Little rascal dog was a pit bull. But, some people turn them into a kind of a land mine, and if you set one off you can get hurt very badly. The police end up shooting some on what seems like a regular basis as there is evidently some dog fighting in the area, and a lot of trash like gangs, drug dealers, and such keeping them.
http://www.cdc.gov/ncipc/duip/dogbreeds.pdf
Breeds of dogs involved in fatal human attacks in the United States between 1979 and 1998