Here’s where I risk coming off as a presumptuous snob. I want to make it clear that I don’t make assumptions about people’s intelligence of maturity level based on which pony is their favorite. This has more to do with the target audience and the people watching with them.
I do think that some of The Mane Five are more complex than others. It’s ultimately a kid’s show, but I think some characters have more to offer for older audiences. For example, Izzy is kind of silly and does crafts, but she also has a quiet wisdom, like in All That Jazz.
And then there’s Zipp. She has the widest emotional range. She stands to lose the most if the crystals fail. Her ongoing story is about repairing her relationship with her mother and sister. She’s a smart introvert without being pigeonholed into “the nerd” or “the shy one”. Then you get into spicy stuff like unconscious desires; she’s rebellious, but deep down she just wants approval.
Zipp goes hard as a character.