Umbriel

Edward would, hands down.

He is the stronger of the two. He knows more (alchemy wise). He knows more secrets, because he has seen the door on more than one occasion. He has a stronger will. Not to say that Alphose's will isn't strong, but Edward's is stronger.

If it were a friendly see who's better battle, Edward would win easily.

If it came down to a battle to the death, Alphonse lacks the fortitude to go the distance against Edward. Edward would go to any length to keep from killing his brother, even to the point of hurting him (really hurting him) to stop the battle.

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Just a note. I believe Alponse never saw the inside of the gate, because Edward fixed her soul to the suit of armor immediately. Where as Edward saw it, because he was almost pulled in, and he opened it again later. He was shown "everything" about alchemy through those moments. He in a sense became connected with the very essence of alchemy. That is why he is able to do alchemy without a circle. That is why he is able to do alchemy that other alchemist could never attempt. He would only grow stronger as he aged.

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