My own favorite is Cure Sunshine / Itsuki Myoudouin (I hope I spelled this right) from Heartcatch Precure (she's the yellow Cure of that show). Seeing how you haven't watched that yet (as I can see from our shared list), I can't say too much without spoiling stuff, but let's just say that her initial internal conflict made her an interesting character (edit: however she becomes a Cure relatively late for Precure standards - after ep.20 iirc - so even telling you she's a Cure was a spoiler by itself I guess - sorry about that). I also liked Cure Marine / Erika Kurumi and Cure Blossom / Tsubomi Hanasaki (again from Heartcatch, the blue and pink Cures respectively) - Erika seemed annoying at first, but I quickly warmed up to her fun character, and liked Tsubomi because I could relate to her character, as I'm similar in some aspects myself.
As for Healin' Good (the only Precure show we've seen in common so far - though I dropped it after 24 episodes as the whole 'Asumi having to learn every single basic concept in order to function in society' got annoying), Nodoka is pretty cool, but I think I preferred Hinata because her character was more fun (she's comparable to Erika character-wise, the difference being that Hinata seems to have some sort of ADD). Having seen Go Princess beforehand (another one you seem to not have seen yet) Chiyu felt to me like a copy of Cure Mermaid / Minami Kaido from that show (also a blue Cure): without spoiling too much I'll just say that their personalities are similar and the sea also plays a part in Minami's backstory (though a much bigger one in her case, as evidenced by her Cure name).
