I thought that an untrained GSD did have it in him to attack was pretty good.
I however think the guy intruder was overly attentive to the dogs. With the GSD he actually waved him back. I'm assuming an intruder wouldn't take that chance. It would have to be a pretty ballsy intruder to keep walking through a house with a dog barking though.
And I don't have dogs for protection. I'd hope they'd deter a break in with their bark, but that's about it.