Rotties if trained and conditioned right will guard the shyt out of your place and attack on instinct if they see you being attacked.
German Shepards are reliable too but the both that I've had over my lifetime developed ear problems to the point where it made them more docile/scared of irritating the ear as opposed to seeing vigilant.
Never had a pincher and I'm not keen on Pits and all the conditioning and training you got to do with em.