I pray that G'man never has to make this decision - you are losing either way. If we replace Cam with a middle of the pack QB we are either better or exactly the same... that's what he is right now: middle of the pack (and passer rating alone says he is significantly worse). If we replace Luke with a middle of the pack mlb we get worse.
I'm optimistic though, I'm hoping a better line, a better WR corp, and a better OC (please!) help Cam up to the elite category.