Pit vs. mastiff? With some breeds it depends more on the dog than the breed. But more so then not a pit will probably win in a dog fight. That is what they were breed for. Most mastiffs where breed to guard and protect. But it really depends on the dog. My johnson american bulldog got in a tussle with my friends pit and I had to get a break stick to get my dogs jaws off my friends pitbulls neck. So it is not written in stone but I would never think a big dog is going to win because of size. A 45 pound pit could kill my 120 pound bull mastiff because she is not bred to fight other dogs. So size really doesn't have alot to do with it. It's all about "gameness".Good website for dog breeds www.moloss.com. And the pepper spray is not a bad place to start if you can't carry handguns in public like here in chicago. It is better than nothing. But once again it really depends on how committed the dog is so no it will not work in all circumstances. In any case the pit should be on a leash especially if it can be agressive and the bottom line is it's the owners fault for letting the situation happen.