I was told back in the late 60's by an ex-con friend of a neighbor that my small dog scared burglers worse than anything. They hear everything and don't mind telling you at all hours of the night and day....and most apt to be house dogs. Large dogs are usually outside dogs and they can take care of them for the price of a steak.
A baseball bat is a great persuader too. 15 yrs ago, I was told by a deputy sheriff that I'd go to prison if I shot someone thru my front door but I could beat their heads to a bloody pulp with a baseball bat if they crawled in a window. (if they live thru it, they can sue and usually win for some strange reason) Never have had to test that theory and I can now use a gun here in FL to protect me and mine. It's a crazy world out there.