>>153422380Okay, so both of them are pretty focused on beating their rivals, Yozora and Yume respectively. They're both near the top of their class and are protagonists. So I'll try and pick apart why they're different.
Let's start with the low hanging fruit. Laura says that nearly everything "gets her going", whereas Mahiru is more passive. If we take this at face value, it means that Laura really is more easily excited and open to a variety of experiences. Compare this to Mahiru, who is a lot more reserved except for one notable exception: her tile breaking. Regardless of whether you like it or not, it shows that Mahiru consciously controls herself, but when she snaps, she really loses it. This difference in self-control is important.
Then there's how perceptive they are, something I personally place a lot of value on. This means how good they are at reading the mood and noticing subtle actions that others take. After Koharu, Mahiru is the second most perceptive, always glancing at Ako's reactions even when the others don't see her. Laura is pretty bad at this, and I'd place her even below Yume. This doesn't show a lack of empathy, but rather a sense of individualistic vs collectivist mindset. It also fits Laura obsessing over her own individuality.
Next is their goals and inspirations. Yume, being the protagonist, obviously admires and chases after Hime. Similarly, Mahiru chases after Yozora, wanting to beat her on her own terms. However, Laura doesn't look up to anybody, instead focusing on herself and her rivalry with Yume. This notable difference makes her more similar to Lily than anyone else, and is a unique character trait in itself.
There are also other minor things such as Mahiru falling into the pampered little sister mode at times, and how she calls out rule breaking but is willing to rehabilitate, or Laura being more lost in finding her own path along the way, but those are probably the major things that make each of them unique.
