I used an essay from another school, and I think it would be very obvious to an ad-com at Yale, think they will know precisely which school's essay I was recycling but I didn't care because the essay was good and captured all the things I wanted it to.
Maybe it's stubborn and stupid of me, but if they give you the option to do whatever you want, I'm not going to reinvent the wheel, so hopefully they don't hold it against me. If they wanted something original they could have come up with a unique question.
It's like Edgerrin James said when he was b*tched out for not going to a voluntary training camp, "Hey, I only went to college for three years , but even I know the meaning of the word voluntary."