Never had Black Australorps but I do like Buff Orpingtons. I think that for a backyard or hobby flock, you really can't go wrong choosing a breed because you like its looks. Yes, some are more docile than others and some like Polish and feather-legged breeds may have issues (mud in the case of feather-legged breeds, rain in the case of crested breeds plus non-crested breeds in a mixed flock may try to pull out the crest feathers), but with a little research I think you can learn about and work around these issues. If you don't want to raise chicks, you might be better off to get a non-broody breed. Even if you don't have a rooster/fertile eggs and don't want to raise chicks, a naturally broody hen may try to set anyway and it's hard to break her of it.