To me it seems that Orton is worse when the pressure is greater. Maybe that's normal, but we obviously need better. I'm not talking pressure by the defense, I mean pressure on him to deliver, because the particular game ("must win"), or circumstance in the game - calls on him to deliver. Hell, he knows if he plays lights out and heroically in those circumstances, he'd be a Bills god and secure his future. Or, the opposite, fail, and the Bills are just one more team in his turnstile career. We got the latter, which is what we should have expected.
If you leave him in now, when the playoff pressure is off, hell, he might start to deliver again, but will we really be learning anything? Why not start EJ, and by the end of the season find out whether he actually has any future with this team. We should pretty much know what we have with Orton by now. He's not the savior riding the white horse.