Go for Wizard. This job has much more versatility -> more AoE spells (Storm Gust, Lord of Vermillion, Meteor Storm), other useful spells like Ice Wall.
Sage is quite... hard to train, and it takes a long time @_@. They have low SP, too, so you might need to sit around often and wait for your SP to recover.
Good thing about sages is: They have some more HP, and they can walk while casting, if you don't have instant cast already.
But either way, for killing lots of things and getting much loot, Wizard is much much better.
