Erwin was drunk on curiosity to understand the world than to save the people within the walls. If he would choose Erwin, Erwin would prioritize his dreams rather than their goal of saving humanity. And then he later says he chose Armin because they pushed Erwin to be a demon.
Was saving Armin the right choice?
Though Captain Smith was clearly believed by many to be the right one to save when it came to the final episodes of season three, its clear that Armin as the Colossal Titan was ultimately the right way to go to save the world.
Who was a better choice Erwin or Armin?
The pro-Armin camp posits that he was a better choice. Erwin himself wasnt aware of what he would do once he found out the truth about his fathers theory. Eren and Mikasa claimed that even Armin was a good strategist and tactician. They cited reasons like his ability to find the identity of the Female Titan.
Who is more powerful Mikasa or Levi?
Since Mikasas a quick-learner, shed easily make the perfect candidate. In summary, my perspective is that Levis stronger than Mikasa due to age and experience. Mikasa grew up in an environment where she had to learn techniques at the pace of other soldiers, despite her strength and ability to learn quickly.