I think Levi cared enough about Erwin not to revive him and have him continue to suffer. Levi put Erwin out of his misery in my opinion. Meanwhile I think Mikasa would've just revived Eren because her programming is extreme.I feel like when he chose Armin he was still following Erwin's orders of "use it wisely" or "I trust you to make the right choice" or whatever he said