I always liked Midna b/c I got the impression she was genuinely moved by your kindness and her growth as a character was something you caused. That said I never understood the Navi hate. I mean she was alright, but I never got why everyone was so mean to her.
She's the best! As for the Navi stuff, I feel like she just didn't age well. OoT was like the first 3D adventure game so she basically has to explain how doors and looking work and nowadays it feels incredibly intrusive and annoying.
I always interpreted Zelda vanishing after healing Midna as her transferring her triforce piece to Midna the only thing that is keeping her corporeal in the twilight shrouded castle. I see her vanishing as her becoming just like every hylian turned spirit and this makes her vulnerable enough that Ganondorf is able to pull her to the throne room as his trophy. Rather than just vanishing into nothingness and supposedly dying.
In the desperate hour, Midna almost dies for you... but during the final stage when she fights Ganon alone, she ACTUALLY dies for you. It doesn't matter if she gets brought back post fight, in that moment she is actually killed after sending Link and Zelda to safety. That sacrifice doesn't go away.
I think Phantom Zelda is better mechanically and certainly very similarly if not more involved. I just feel that Midna is much more well written and a better character in the grand scheme of things despite Zelda still being crazy well written.