In general, they will not consider each other as competitors, enemies, or friends. That won't mean their personalities won't clash. Given enough space, well and properly fed and cared for, they will be fine.
It's basically going to come down to tank size. These two angels will normally ignore each other when housed appropriately. Lee's point on the "personality" of the fish being the one mitigating factor. The Swallowtail does need a good amount of swimming room though.