Actually, Zoom, Filas aren't really stranger "aggressive." They ARE very distrustful and defensive with strangers. Very, very few will aggress, but they will warn a stranger not to trespass in their space or get too near their family. That's just one of those fine points that you almost have to live with a dog to understand though, but we do try to educate non-Fila owners (and some owners) to the difference, as it's really NOT the kind of reputation that responsible Fila owners want to engender 
You're right on the money with the Bulls. They are probably the least affable of the Mastiffs when it comes to other dogs. They are intelligent and will usually accept the family dogs as part of their family, but dogs outside their immediate family are just NOT the Bull Mastiff's cup of tea at all It makes sense when you think about how these dogs were used against poachers . . . and many poachers had hunting dogs with them.
You're right on the money with the Bulls. They are probably the least affable of the Mastiffs when it comes to other dogs. They are intelligent and will usually accept the family dogs as part of their family, but dogs outside their immediate family are just NOT the Bull Mastiff's cup of tea at all
It makes sense when you think about how these dogs were used against poachers . . . and many poachers had hunting dogs with them.