Are Limits and weapons that important if their sole purpose is to be a mage? Anyway, using MP will reduce the power of Red's Limited Moon while Vincent's remains constant, although it takes a while to power up.

I also think that Red's Stardust Ray (Lv2-2) is better than Earth Rave as it hits twice as many times. Each hit is weaker, but once you've used a couple of Hero Drinks it will deal a decent amount of damage.