Well familiar with other 'large' working breeds such as the Doberman Pinscher and Boxer...always been a fan of the APBT, but have not had the opportunity to enjoy one until recently.
Otherwise, we generally avoid small breeds; but have found 15+ lbs Rat Terriers to be fairly tolerable. Typical terrier attitude so they still have a bit of the Little Dog syndrome; however, no where as bad as your average Chihuahua LOL.
Altogether, we currently have a Pit Bull (still uncertain on whether it is APBT or AmStaff) and a Rat Terrier. Two cats...a Savannah and Bengal. And dozens and dozens of African Cichlids.