Roethlisberger: Better QB, at home.
Kitna: Steeler defense might smother Carolina so much Steelers don't throw, while bad Dallas defense might force the offense to score more. Carolina's pass defense is the least bad aspect of their team, while Arizona's is as bad as everything else.
I'd start Kitna, but it'd be reasonable to go the other way. Also, you should always be wary of any advice coming from me involving Cowboys - I'm biased and know it.