I think "not as frequently" is a understatement. Cats are orders of magnitudes less dangerous to humans than dogs are, it's not even something I have to think about when I walk outside. Meanwhile, often times, the only thing that stops a dog from attacking me is the gate of their owner's house. Even that won't stop them from running at me and barking at me though. And yes, I've walked by a house with no gate before and two dogs just came after me and attacked my legs, one even biting me. I'm no dog hater or anything, in fact I like dogs, but dogs are only appreciable if they're on your side. I shudder at the thought that anyone would be able to get a pitbull and do whatever they please with it without licensing or repercussions for letting it loose on the neighborhood children.

EDIT: Forgot to say, it don't matter even one bit what size the dog is or how small it is. If they aren't on your side, they're capable and very willing to bark at and attack you.