I only have one Cochin and she hasn't laid yet. And is very standoffish. My two Buff Orpingtons are excellant layers. they also are standoffish...but since I don't have a roo I don't know about brooding ability. However, I've read that cochins make good mother hens and a lot of people use them as brooding hens..
I only had one buff orpington and she does of sickness before she even laid her first egg.... My Cochin hen has raised one chick (it was one chick out of two eggs) and she was fiercely protective of it. She never let a piece of fluff of his head be harmed. (Although he rubbed a bald spot on his head getting out of the egg so he didn't have much fluff up there to begin with!!) She let him pick food off of her beak, and one of my other hens tried picking food off her beak, and the Cochin snapped! I find this funny because my Cochin is tiny, and the other hen is big!!