Do you want your dog to be a watch dog? First, let's define the way I'm using the term. A watchdog barks when he sees or hears someone or something near his property. Because every breed can and usually will bark or offer some kind of alerting behavior, every breed is a potential watchdog. Some breeds are more consistently watchful than others, but when an individual dog happens not to be alet to strangers, that is usually the individual, not the breed.
The majority of burglars will shy away from homes in which any dog is barking. THus, even the barking of a little dog or a friendly dog whose bark is one of welcome rather than warning is all the "watching" that most families need. If you're looking for a dog whose appearance and behavior would give burglars even greater incentive to stay away, choose a medium or large or giant dog who looks imposing and who is aloof with strangers.
Now, if you're looking for a dog who is inclined to do more than bark, please consider the following: Some breeds are naturally protective, but they must be taught how to protect, i.e., where and whn to bite. Professional training is expensive, and the result is the equivalent of a loaded gun. Guns often do more damage to the innocent than to the guilty, and a dog has no safety catch and connot be unloaded. (Proponents of guard dogs argue that a dog, unlike a bullet, can be recalled, but they will also agree that few dogs are that well trained.) And training carries no guarantee of protection because a professional criminal has many ways of dealing with a trained dog: Mace or a bullet, for example.
Perhaps you want a naturally protective breed but don't want to gog to the trouble and expense of professional training. Perhaps you believe that an untrained Doberman will protect you "naturally." You may be in for a shock. Let's say the burglar isn't even a professional with a gun. Let's say he simply ignores your barking Doberman and breaks into your house, where he's promptly bitten. Don't you agree that a man who was already bold enough to enter a home in which a big Doberman is barking is going to fight back?
You bet he is. And since an untrained dog usually bites at the leg, the burglar, with both hands free, will knock your beloved dog's brains out wiht the nearest chair, or stab him with a pocketknife. A few really tough dogs might continue to make a fight of it, but most inexperienced dogs who suddenly find themselves in a real fight with a human being will back down. NOw the tables have turned as the angry burglar chases your bewildered dog with murderous intient.
Many a protective dog has lost his life trying to defind his owner's TV set, while the dog who is "so friendly he'd escort the burglar to the silverware" escapes unharmed. Thus it can be a disadvantage to own a protective breed, for no TV set is worth serious injury or death to a dog who is a member of your family.
But what if it's not your home and propertyl that is endangeed, but yourself - by, say, a mugger on the street? WOuldn't you want your dog to protect you then? Actually, he may not have to, because most muggers, like most burglars, will shy away form anyone whith a dog. Dogs can bark, and barking draws unwanted attention. But if you believe firmly in self-defense and you want your protective dog to be similarly equipped, consider joining a Schutzhund club. Schutzhund is a rigorous German sport that combines tracking, obedience, and protection. The training is exciting, and the result is a dog-owner team that works together in a close relationship.
Final recommendation: If all you want is a dog who barks or otherwise alerts you that people are approaching, you can make your choice from among all the breeds. But if you must have a breed with some size, muscle, and a reputation for defending his home and family, read the profiles carefully to see what is said about protective instincts and terrioriality. Unless it is specifically mentioned, a breed should be considered to be only average or below in these areas.
Once you've gone ahead and brought home your protective breed, don't ever allow him to threaten anyone. Let him serve as an imposing presence that will discourage most criminals, but reassure yourself that he will never die because hs actually bit a criminal who then called his bluff.