Quote Originally Posted by Pit Chick
One can go insane trying to find the differences in the two breeds, but there aren't any. A show bred Am. Staff can look exactly like a show bred Pit Bull and they can be duel registered as either breed. Nothing was added to either breed to make them different. The AKC recognized Pits Bulls back in the 1930's but changed the name to Staffordshire Terriers to disassociate themselves from dogfighting. Physical appearance can be slightly different depending on who's breeding. A show bred Pit or Staff will have bigger broader muscles while a working or fighting bred Pit will have leaner, toner muslces. Ear size varies depending on why they wanted it cropped.
From my time in the dog show world when I showed my collie, this is pretty much how I understood it after chatting with some other show people when I asked about it as I found it confusing. It can be confusing and you can read around and have people say yes they are or no they aren't, but the fact that they can be dual registered pretty much means that basically they are. From the history I read about Amstaffs, it is like you said, people wanted to disassociate the show/family dogs they were breeding from "pit bulls" so the AKC officially recognized them as Amstaffs instead of APBT. Fighting line pits can look different from show bred the same as racing greyhounds look different from an AKC show greyhound, they are bred for performance rather than to a physical standard.