I would get a nice social, happy dog that isn't going to **** off your neighbors barking all the time. A dog you'll love as a pet and you can love and snuggle all you want. Then get a security alarm or at least some cheap security stickers to put on your windows to bluff your past any bad characters that might be coming your way.
I doubt you want the responsibility of owning a protection dog and I certainly wouldn't put my life in the hands of a dog not tested. Get a dog you'll love and if somebody is around that shouldn't be, they might bark they might not.
my dogs rarely bark, one the rare occasion somebody walks thru our yard at night, its low toned woofs, but if anybody's arm should come thru a window i'm sure they'll be in a hurry to get back out as soon as they can. When I'm not home they bark more, my neighbors tell me cause it suprises them that whenever i'm home and they come over they never make a noise, but if they come over and i'm not home even though they've played with my dogs they won't dream of opening the door because of the sounds coming from the other side.
Dogs that bark at lots movements that have little barks don't scare many people, and just annoy your neighbors, dogs that have big barks and are confident dont' bark that often, big dogs that have big barks that alert bark often really **** off your neighbors.
so, yeah, my opinion, just get a dog that has a good temperment and one you can live with and get an alarm system, or some "this house protected by smith and wesson" stickers.