No idea why people insist on those aggressive races... There are a lot of other dogs which are loyal, will protect you and your property much better than the races mentioned, and are a lot calmer and easier to be controlled.
Of course one can mention that its not the race of the dog, its the way its brought up and trained, but still, pits and staffs are fighting dogs, its their purpose and thats how they've been bred. You never know when nature calls and your pit rips another dog to shreds with all legal consequences involved.
I love caucasian shepherds for example and huskies (only get the latter if you have a lot of space for him to run around - DO NOT keep it inside!) for example, some other races (dont know their names in English), but i would NEVER get a pitbull or amstaff.