SCH AOE DPS is far better. Single Target they are about the same, with the asterisk AST can't keep it up. DPSing on AST runs AST out of mana in pretty short order, whereas SCH can go indefinitely. It presents a major problem in fights there the offhealer spends the first 90sec or so dpsing. You aren't totally OOM after as an AST, but your mana level is very unsafe.