I wouldn't really compare the two as they are two different classes unless you're looking at clean stats. In that case then Mages win out over Bishops in most cases but you see this whenever you compare a hybrid class to its "parent" class.
Eterna base skill heals allies, Odette decreases incoming magick damage. Eterna SAW'ed heals and attacks enemies for less attack and Odette SAW'ed decreases enemy magick resistance making her hit harder. Regardless of how you look at it Odette beats Eterna in stats. As I said though this is nearly always the case. Bishops also focus on healing something Mages can't do. It really depends on what you want and need.