I care more about the character designs of the romanceable characters.
After all, they're the characters I'm going to pursue and hopefully fall in love with during the game.
That said, the heroine's character design is important to me as well.
I've played several otome games, and most heroines are very cute, so I usually grow attached to them too.
However, character design isn't the most important thing to me. I care more about the story, the voice acting, and the characters' personalities and actions.