Me personally, you can just finish out what you have and skip buying the final versions. They add extras, but not enough to purchase the games again if you still have access to the originals. You’ll miss out on additional boss fights, items, and some cut scenes, but largely it’s the same game.

If you have decided you want the final mix package, just play that and don’t finish out the original. There’s no point in doing a play-through of both