The American Staffordshire Terrier is a little larger on average: about 25 kg (55 lb) as an adult, against 20 kg (44 lb) for the American Pit Bull Terrier.
Temperament
They differ most on activity (American Pit Bull Terrier: needs lots of exercise; American Staffordshire Terrier: a good daily walk and play).
Alike
Both are rated the same on affection: a lap or leaning dog.
Neither is the better dog in general. Which suits you depends on your home, your days and the care you can give.
Breed explains only about 9% of how individual dogs differ in behaviour7. Meet the dog. A good breeder breeds for temperament as well as health, and matches each puppy's personality to the right home8,9.
Puppy growth
Reference curves · both sexes
Summary
Detail
The American Staffordshire Terrier grows to the heavier adult, about 25 kg against the American Pit Bull Terrier's 20 kg.
Expected weight in kilograms, both sexes: each breed's adult weight grown along the 15–30 kg band of a WALTHAM growth standard10 and the 15–30 kg band of a WALTHAM growth standard10.