Do you believe that pit-bulls are unbeatable dogs in a dog on dog altercation?

Around here when anyone wants to have a dog they feel can defend them on walks, defend their property, or defend their illegal pot growing they want go get a pit bull, or several of them, because they believe the only other dog that can best a pit bull if another dog attacked them, would be another pit bull. Are pit bulls the top of the food chain dog wise? Are they really that invincible that no matter what breed or size of another dog, a pit bull can beat them?