I actually think Ariana is also good at showing off parts of her personality. She's a beautiful dancer. And I kind of like that she's often out-of-breath at the end of her dances.
As for Charity, she definitely needs to learn how to connect to the audience better, but that's a really hard thing to figure out if you don't even know where to start. She could've grown up that way and maybe it continued for her entire life. It's not always something that you can just figure out in a couple of weeks.