Yikes...I probably wouldn't touch either of them, even late round/undrafted. Chad Kelly looks like he could be a headcase and Seth Russell would need to be completely developed from scratch because of his Baylor system background and he doesn't have the experience that RG3 and Bryce Petty had either.
Between the two, I go Russell. Beyond being hurt, Kelly is also clearly an idiot.
I'm still on the Gunner Kiel wagon, which at this point barely has wheels.