Yuma was often compared unfavorably to Malal (which I doubt was good for her self-esteem). That said, she was told that even Malal (without assistance) couldn’t have used Cavefish as an expendable power source like Yuma presumably did. What things could Yuma do that Malal couldn’t?

Yuma basically had the Culexus equivalent of power vampirism, where she can utilize someone's magical energy and use it alongside her own. She can also do it passively if she's in a large group or unit, taking just a little bit from each member in the group, so it's kind of like a force multiplier.
Besides that, Yuma also developed the ability to completely make herself disappear in a magical girl's radar. Callidus, Vindicare or even other Culexus wouldn't be able to detect her. It's more of an Anti-Officio Espionage kind of deal, so it doesn't work with Witches.