Socialization is key whichever breed is chosen, and it varies dog to dog. My Presa and Dogue both bark, check out who I let in, (sniff etc.) then usually my presa will get a toy and will want to play. And they both love kids, and cant wait for my daughters friends to come over to play. Now of course if the scenario is different and someone is forcably trying to enter my home with or without my family there, there will some problems. Most dogs, Mastiffs especially will flee rather than stand up and fight anyway, and there is no way of knowing what your dog will do unless put in certain, stressful, fight or flight type of situations. I.E. temperament tests etc. I know my Presa when challenged will Not back down, my Dogue however intimidating she might look to some, backed down. Like Jase said in the opening Post, he wants a dog to be able to attack not just stand and bark, so you have to weigh in that need as well. Very few breeds will engage when challenged, again, find a reputable breeder who breeds the "working lines" of the animal, not just for size or conformation.
