The Bull Terrier and Miniature Bull Terrier are two extremely similar and closely related dog breeds. For a very long time, they belonged to the same collective breed, but recently, in 1990s, they were recognized as two separate breeds by the AKC.
Many people believe, that the Miniature Bull Terrier is a downsized version of the Bull Terrier, but that is not true. In reality, the first Bull Terriers that were developed in 19th century England were about the same size as the modern day Mini Bull Terrier. Some breeders wanted to increase the size of this breed, so they crossed it with a Spanish Pointer and possibly some other breeds, which resulted in modern day Bull Terrier.
So indeed, the Miniature Bull Terrier pre-dates the „standard“ Bull Terrier and it is the older breed.
So as you can see, these two dogs are extremely closely related together, and even the American Kennel Club say, that except the size, these dogs are almost identical in every other aspect, including appearance, temperament and maintenance.
It is true, that on a single photo, it is impossible to say, if it is a Miniature or Standard Bull terrier. You can only see the difference, when they stand next to each other, just like on this photo. The average height of the Mini Bull Terrier is between 10-14 inch, which is 25-35 cm and height of Bull Terrier is typically somewhere around 21 or 22 inch, which is 53 to 55 cm. Breed standards do not say anything about the weight, but it should be proportional to the body.
There is no other real difference in the appearance of these two dog breeds. They both have the typical egg shaped head, muscular body, triangular ears and both come in wide spectrum of colors.
The temperament of these two breeds is also identical. Both breeds are described as energetic and lively, courageous, full of spirit and with fun loving attitude. They are very friendly with its family, but if socialized properly, they are friendly with almost everyone. Some might be independent and kind of stubborn, which is the main reason why they are not the perfect fit for unexperienced dog owners. They are perfect family dogs, as they typically absolutely love children and they are devoted to the whole family. This description applies to both breeds and there really is not difference between the temperament of Miniature Bull Terrier and Bull Terrier.
Of course, the Miniature Bull Terrier is little bit more manageable, as they need little bit less of exercise and they can live in smaller space. But they are still active dogs, neither of those breeds are coach potatoes, but it is true that the larger Bull Terrier needs little bit more exercise.
Both breeds are also very easy to maintain, as they do not need almost any grooming at all. You should only brush the coat from time to time to keep it in best possible condition. And thats it, no other grooming is required.
In conclusion, there really is not much difference except the size in those two breeds. So if you are choosing between them, you should only look at the size. If you prefer smaller dog, than go for Miniature Bull Terrier, but if you like medium sized breeds, than go for the normal Bull Terrier.