My dog is pretty damn big and he does scare a lot of people (photo attached) being 8 stone and as tall as me when on his hind legs (I'm 5 ft 8"), but he's very well trained and therefore an excellent guard dog.
Admission time ... I'm actually a qualified dog trainer in my spare time and run a weekly training club for the Kennel Club. I don't think I've ever mentioned that on here. We're a very busy and popular club. Tonight I trained 40 dogs and handlers.
My favourite dogs are the ones whose handlers researched their breed and chose a breed that suits their lifestyle. I've seen some amazing small dogs who I would gladly own tomorrow even though I prefer large - giant breeds, but its usually down to the handler going to a good breeder.
The worst dogs in my opinion are working strain collies and gun dogs cooped up in suburban homes or with inactive people - such a shame for all involved