I have a Dobermann, and she is a good protector. The problem is that she is everything to me, and the desire is for me to protect her. I do feel that a good defense is the best solution. Securing windows and locking doors seems like the most important thing, and not doing that is the most common way people get in.
I have heard that the theft rate for people on the ground floor is actually less, because owners/renters are more careful with windows and doors. Thieves know this and will often target upper floors, because it is easier and people are less careful.
I do have a peephole, but I am thinking of adding a camera. That way I could selectively open the door. I can do that now, but there is enough noise walking to the peephole, that someone would still know if I came to the door.