No dog is worse than another.
They all turn: chihuahua's, rottweilers, labradors.
And there are no bad dog's, only bad owners (such as applies with kids and parents: no bad kids....)
It's how they are raised.
The thing of it, is this:
If a chihuahua attacks your pant leg going full throttle, you can shake him off and laugh at him pitifully.
If a rottie attacks your leg.......
They are bigger dogs with powerful jaws. If you can't control them....
OF COURSE a bigger dog with more strength can "be" dangerous, but doesn't mean that they are, if that makes sense.
And ANY dog will 'turn'.
My Nana's best friend had a golden lab. Sweetest thing. Played great with kids, we pulled his tail and everything. Never so much as a snap.
When I was 4yrs old, he was asleep on the floor. I tripped and fell on him and startled him..
Next thing we all knew, my face was in his mouth. (thankfully, no scarring)
Hardly his fault, I scared the crap outta him and had probably hurt him when I landed on him.
I also had a friend with two pittbulls.. sweetest things. Absolutley DARLING. Great with the kids.. etc.
My neighbor has a poodle? I would GLADLY drop-kick that nasty thing. Growls at my kids all the time, they can't pet him cause he snaps. BUT that's the owner's fault.
I have seen similar with my own pekeingese when my 4yr old fell on him when he was sleeping... he snapped and grazed her cheek.
AND he is the MOST darling sweetest thing, wouldn't hurt a fly, loves everyone, would probably lick a burgular to death, and he sleeps with the cat.
In my own experience, I have actually seen more nasty SMALL dogs than big dogs. (years ago, did door to door sales... LOTS OF DOGS and my leg DID get attacked by a chihuahua, funniest story:lol: ). I have found - and a vet is likely to repeat the same - that most small dogs are often immediately on the offense because of their diminutive size & because they feel intimidated, and then will often show aggression first.
Larger dogs, because of their 'confidence' for lack of a better word, will wait until something happens before showing aggression. They don't have to be on the offensive, so they are on the defensive. They aren't afraid, they aren't nervous, they aren't intimidated. In my travels, in my own experience with my own dogs (large and small) and experience with friend's and family's dogs... I worry more about the wee ones than the large ones.
Granted, there are also different personalities in animals such as with people.
BUT if an animal shows an aggressive side as a puppy then it's the owners responsibility to train him appropriately. (just as kids are corrected not to hit other kids).
And you can have the 'odd' animal that's a bit unstable SAME as with people (maybe due to inbreeding? bad rearing, imbalance, previous abuse, who knows..)
BUT generally speaking, on the whole - there are no dangerous or bad dogs. Just dangerous or bad owners.