For the OP:
Please also note that many burglars poison dogs to get around them - a quick and quiet way to deal with them. I know several people here in HK who have had their dogs (including large guarding types) poisoned in the home prior to a break in. I've heard of many more cases of dog poisonings in the home while volunteering for animal welfare agencies here. I'm not saying that a dog isn't somewhat of a deterrant, but it is pretty easy for even an unsophisticated criminal to get around.
Regarding breed/ type of dog - you seem to suggest that you are looking for a true guard dog to patrol your property. Getting a pup and training it yourself to roam around for intruders / protect your property will not likely work unless you have extensive experience in training guarding dogs...the process is very time consuming and expensive. If you just want a dog to bark if it sees something unusual, not sure why you have picked the two breeds that you have.
Also, even a mean looking big dog won't necessarily protect your place. Until a dog is actually challenged you really can't predict how it will react. There are plenty of scardy cat type German shepherds, dobermans, etc. out there and this is a trait you cannot necessarily pick out from puppyhood. True "guarding" dogs are trained for years and numerous dogs "flunk" out of guard dog school because they lack the temperment.