The DC movies have a problem with trying to make each movie feel very different from the others. Director James Wan spoke to ComicBook.com about how he planned to make Aquaman different from Superman in particular.
"Well, I think firstly one thing I've been very cautious about doing is making sure that he isn't Superman," Wan explained. "From a story standpoint there's a reason why Aquaman ultimately is powerful. He's strong because, like most Atlanteans, their bodies are built to withstand thousands of pounds of pressure, they live so far down. So when they come up, their body is… they're not aliens from another planet, but because of the physics of our planet and all that stuff, when they come up to the surface world their body can withstand really strong pressure. And so where bullets literally bounce off the Man of Steel, bullets can graze these guys and maybe break the skin, and break the flesh, but it doesn't necessarily penetrate because they their muscle mass and their body mass is much more dense. Even within the world of superheroes I try to find a reason for why how he is the way he is. So he can get beaten up. When he goes up, surface world weapons may have a hard time taking him down, but Atlantian technology can cripple him for sure. It can really destroy him."
So it sounds like Wan isn't comparing Aquaman and Superman as far as personality goes, but more along the lines of power sets. People are going to be doing the "who would win in a fight" thing no matter what anyone says, so Wan is just trying to get rid of those pointless conversations ahead of time.
Summary: Arthur Curry learns that he is the heir to the underwater kingdom of Atlantis, and must step forward to lead his people and to be a hero to the world.
Aquaman, directed by James Wan, stars Jason Momoa, Amber Heard, Nicole Kidman, Patrick Wilson, and Willem Dafoe. It will be released December 21st.