I reckon having a guard or watch dog always carries a risk. If you want a dog that will actually show aggression towards intruders, you might not be able to trust them around any stranger. If you want a dog that barks at potential intruders, you might end up with a nuisance barker.
BUT... for most intruders it's enough for there to be a dog. Unless they are very keen, as in they know that there's lots of valuable stuff in your house, they won't risk finding out that your dog has a taste for human flesh after they went through your gate. Even if the dog is wagging his whole body when he spots them. You just never know.
And as mentioned by a few others, whichever dog you end up getting, make sure you learn about training (even if you have had a dog before, you should never stop learning), make sure you make time to train and exercise and if you want a dog that you can easily take places and never gets you into trouble with other dog owners, socialisation is so very, very important.