I've had both breeds over the years (still have Black Australorps), and while both are excellent breeds, I personally prefer the Australorps. While both breeds are generally docile, I have on rare occasion had an aggressive Barred Rock. I've never had an aggressive Australorp (of course there can always be an exception with any breed), and my children had an easier time making lap pets of our Australorps than they did our Barred Rocks. Both breeds are very cold hardy, but Australorps handle heat better. I raised both breeds in CA where summer temperatures frequently reached 117-118 F (123 F once), and while my Barred Rocks were panting and holding their wings outward, my Black Australorps were going about their business as normal. And most importantly for me, Australorps are a little better layers than Barred Rocks. I typically get 5 eggs (occasionally 6) per hen per week from my Black Australorps, but usually only got 3 eggs (sometimes 4) per hen per week from my Barred Rocks. A Black Australorp holds the brown egg laying record with 364 eggs in 365 days, and while I have never had that kind of production from mine (and likely never will), I have still had a few of them lay over 300 eggs in a year. Barred Rocks are a great breed, but given the straight up comparisons, I think the Australorps are slightly superior, at least in meeting my personal criteria for a breed.
