I think Amane needs more character growth. For now, what she has going for herself is.... that she is an Otaku. Sure she's also pretty, and nice to him. But that's it.
Ijichi is pretty, smart, cheerful, kind, willing to try just about anything when she is with him. She's just a more rounded character.
Regardless, they're both wholesome and nice and I hope for an ending where nobody gets hurt.
The way I see is Amane is on the same wavelength as the MC. She doesn't just have the same interests, but a lot of the same faults too. She comes off as a lot more human and immature.
In the other hand Ijichi is a lot more mature and nurturing. She's not on their wavelength automatically, but can adapt herself very well and she offers different insights and traits that neither really have. At the same time this means she has to try harder to enjoy the same things as our MC does or that she ends up pushing him to do new things. Neither of which are neccesarily good or bad, but she so far does it in a great way.
I mean none of the traits you mentioned about Ijichi actually denote more or less character development. They're just nice traits. They both have pretty equal character development (we know their home life and how they act defensively, we can get to their core traits, we know at least some reasons behind those traits, etc). Ijichi has more of a nurturing side like a home maker, but Amane is more easy going and immature like the MC. It's not just kiramon interests. It's stuff like forgetting to do her summer homework or needing studying. What's also neat to pick up on is that's like the OPPOSITE you'd think from their initial appearance. I'll pretty sure in universe people think the "cool" Amane is more mature while the "flasy and outgoing" Ijichi is more immature.
But yeah, all that to say you're not describing character development, you're describing maturity. Which sounds like a winning trait, but I mean they're high school and at the end of the day you'd want to be with someone you can feel comfortable with and vulnerable around. I'd actually be able to choose (in this case Amane) if we saw Ijichi struggling more to match her feelings for the MC. That kind of mindset can actually unhealthy for a relationship (if one person is forcing themselves), but we happily see that they do a good job of balancing. If you have definitively chosen Ijichi for those traits though, that makes sense. She has a lot people generally look for in a partner.