Tiana was my first favorite because she was the first black Disney Princess and I saw myself in her as a 4-year-old (still inspires me to this day)
I also really like Rapunzel, Belle, and Ariel (mostly because I had a phase where I was OBSESSED with mermaids. Probably about 7-13 lol).
But my current favorite is Anna. She's so admirable and brave. Even when I was younger, I liked her more than Elsa because she sacrificed so much for her sister and almost died. Multiple times. Elsa was just cool because she had powers. Or maybe I didn't think like that as a 7/8 year old. I probably just thought that she would feel left out because everyone was always choosing Elsa all the time.
After Frozen II, my respect for Anna went up exponentially (though mine for Elsa went up some too)