You'll get a lot of different advice here, I warrant. People have different fave breeds
When I first started out I got Buff Orpingtons and Black Australorps, then later got some Wyandottes and now am completely hooked on Wyandottes. The three are pretty similar kinds of birds in my view, as are Sussex, and Welsummer. Probably others that I can't think of right now.
I can warmly recommend Wyandottes, though mine are breeder birds. I've read elsewhere on the forum that some people have bad experience with their hatchery Wyandottes (uncorrect type & unfriendly, though good layers). My Wyandottes are pretty consistent layers, and have nice temperament.
You might also consider just adding another color Orpington if you're sold on the breed - I've seen pictures of all sorts of pretty colours like Jubilee and Gold Laced.
Best of luck in your choosing!