Can't really compare them. Two completely different players with completely different strengths, playing in completely different offenses.
I guess the only way to compare would be to rate each particular player's success within their offense. And if that's the case, I believe Bray will be more successful in what he does in our offense than Relf will be in his. If Relf was a more efficient passer, then it might be more debatable. But Relf is the definition of a system QB. Good athlete with below average passing ability.