I'd go with the SS for a solid majority too.
Penance stare is inconsistant. Does it just make the victim suffer all the pain she's caused regardless of the morality of her acitions? If there is a moral component to it, who defines what is wrong? Is it the victm's own sense of morality? Do they need to feel some sort of repressed guilt to be affected? Is it the host's or the angel of vengeance's morality? His empowering god's morality?
In his recent run there was a guy, some zadkiel worshipping fannatic, who shrugged of the penance stare claiming he did not regret any of his crimes as they were god's work - he was on some kind of angelic steroids when it happ ened, so that may be the actual cause of his immunity though