Is there a difference between a little dog and a big dog? Well the obvious answer would be heck yeah. But really is there? Beside the obvious.
Little chihuahua v. a South African Boer Boel (by the way is a 150 lb dog full grown). Both need to learn to go potty outside, both need to learn where to eat, what is okay to eat, sit, stay, wait etc. So both are dogs. They both need to learn the same lessons in life, so far the only difference is size.
Now you are walking down the street and you come across a sweet little 3 and a half pound chihuahua and OMG how cute is that. You stop, can I pet your dog, is he or she nice, because you never know what you are going to get with a chihuahua. They are most likely going to be protective of there owners, we have all seen it, those nasty, nasty Chihuahuas. Okay same situation with the 150 pound Boer Boel, Holy S**T, OMG, what kind of dog is that???? Most people are very interested in this dog because quite frankly how often do you see one. But most will be afraid. Would you? I would not be but I am very into dogs and happen to be very close to a chihuahua and a South African Boer Boel. But that's me, the average person is not exposed to these extremes.
But I am off the point, are they different? Just because one is small and one is big. Are they different because they were bred for different things decades ago? Most dogs don't do their original jobs they were bred for. Are they different? I don't think so. There is one big difference and only one, (in this humble blogger opinion) Size!!!!!! I can still pick up my 3 and 1/2 pound chihuahua TJ (Theodore James) and cannot pick my 150 pound Boer Boel Tank (aka Tanky Boy). But to me they are the same. I expect them both to have manners in public, I expect them both to sit on command and I understand they both need their Leader to love them.
So the moral of this story children is, teach your dogs manners, they will love you for it.