I've raised both breeds for years (still have them) and the qualities of the two breeds are virtually identical (not surprising since Australorps were originally bred using Orpington stock with the goal of improving their laying rate. Both breeds are calm and gentle (my children, and now my granddaughter, made lap pets of both breeds). In my opinion the Orpingtons are slightly the prettier bird due to some of their color varieties, but if you are going to raise only one breed, I slightly prefer the Australorps for the following two reasons. First, Australorps are the superior layers. My Orpingtons typically give me 3, sometimes 4 eggs per hen per week, whereas my Australorps typically give me 5-6 eggs per hen per week. A Black Australorp holds the brown egg laying record with 364 eggs in 365 days. Second, while both breeds are very cold hardy, Australorps are more heat resistant. I raised both breeds in CA where summer temperatures frequently reached 117-118 F (123 F once), and while my Orpingtons (and my other dual purpose breeds as well) were listless, panting, and holding their wings outward, my Australorps went about their business like troopers.
