Ro was a good little Starfleet officer by the time DS9 rolled around. She would stand with Sisko and support the idea of Bajorans joining the Federation. With Kira, though, they had the chance to have a command-level officer with a different agenda.
Kira did end up supporting Federation membership pretty quickly, though. She was always a proud Bajoran patriot, while Ro seemed ashamed of being Bajoran. I suppose that would've been her
arc, growing to appreciate the people and culture she had run from earlier.