I don't know about the key stuff, I haven't read the manga. The storylines sound really muddled from the both anime series which I quite enjoyed so I'm avoiding the manga.

Haruka wasn't given a lot of opportunity to be liked in My HiME, imho. We knew why Yukino liked her when we got a glimpse into their past but other than that she was a peripheral character who just annoyed the main characters. It didn't give her a lot of chance. My Otome does what My HiME should have done with her character, I think. I also like how My Otome improves Yukino's confidence, she's much more take charge in that series which is also why I prefer their characterizations in My Otome to My HiME.

I'm amused by Haruka's relationship with Sara Gallagher too. Sara has that same fond bemusement when she talks to Haruka that Yukino does. Makes me wonder if Sara was Haruka's heya-gakari when they went to school.

Chie is amusing but it's hard to take he seriously with the little magician's outfit. It reminds me of Zatanna on Batman. lol. Lena Sayers is the designated Otome bad ass. Sifr was worthwhile just to see her fight.