Poodle, really isn't about which can be meaner but just the reality that pit bulls have very strong jaws. If they bite down they don't have to let go.
We had a Border Collie and a small terrier years ago. The terrier had very strong jaws, you could pick her up with a sock. When they played tug-of-war the border collie always lost because she had to readjust her bite.
My understanding is that pit bulls have jaws stronger than almost any other breed.