At the age of fifteen, Natasha Yar (played by Denise Crosby) left the anarchic violence of her home world behind on board a Starfleet vessel. When we first meet her, she's chief of security on the Enterprise, a formidable fighter, and a courageous woman. More importantly, because of her background, she appreciates the compassionate, cooperative, rational world of The Federation and has little time to waste with idiots who cannot do the same. In fact, she dies because she refuses to dither around with the baiting, idiotic, mysterious asshole Armus while two of her ship mates might be dying.
DO NOT FEED THE TROLLS!
Ro Laren (played by Michelle Forbes) is a Bajoran. Years ago, Cardassians conquered her people, driving many of them from their homes to become a disenfranchised diaspora. When she was a child, she was forced to watch Cardassians interrogate, beat, and kill her father. Ro Laren is angry and ashamed of her people for their status, and it drives her to do everything she can to solve problems on her own, ignoring the virtue of patience, the voices of experiences, and the help of others.
People make fun of Batman for the influence of his parents’ death on his mythos, but if Ro was a character in the DC Universe, she would be the over-the-top Batman, screaming about the death of her parents at every turn. In fact, I want a Dark Knight Returns movie written by Scott Kurtz with Michelle Forbes unapologetically playing the role of Bruce Wayne/Batman. Get this done internet. Well, hey, I’m always looking to commission artists to create the things I imagine, so maybe I’ll do that one day.
"I am the night, Captain Picard."
Eventually, Ro betrays Starfleet and joins the anti-Cardassian rebel group, The Maquis.
I can't deny that Kira is based on Ro (they wanted Michelle Forbes to be in Deep Space Nine, but she declined.) or take refuge in the fact that for every two episodes that either Yar or Ro were pictured in--even via clip-show or hologram--Kira was a main character in nine, giving her slightly more development.
*Alright, not technically ten years, but I don't invoke Grosse Point Blank lightly.
Yar and Ro both left their bad situations behind and joined Starfleet. Yar did it because it represented something better than the world she grew up in. She believes in The Federation because she sees the good that it can do. It gives her a picture of a brighter alternative and the potential of mankind. Instead of just curling up and hating the universe for not doing enough to make itself a better place, Yar engages it and improves upon it. Ro Laren wants flee her people and break the cycle of victimhood by being a dick and acting more "real" than everyone else in super-white suburbia that The Federation sometimes seems like.
My point is, if she hadn't gotten killed trying to save two shipmates, Tasha Yar would've snapped Ro in half like a wrinkle-nosed slim-jim(TM) thirty seconds after she came on board. If Ro Laren was Batman, then she's this one.
Ro Laren blames her people for being beaten by the Cardassians and blames The Federation for not doing more to help. She blames The Cardassians too, but until she joins The Maquis, Ro Laren doesn't give a single fuck about helping Bajor or the Bajorans, above gabbing to others about how they aren’t helping enough. She's a pissed off teenager looking for the opportunity to rebel because she believes it will make everyone sorry they see how obvious wrong they were for ignoring her all the time. Meanwhile, no one cares except for some self-recrimination over trusting her.
Pretty much this.
Kira Nerys fought to expel The Cardassians from her planet every day. She never lost faith in her people or in The Prophets. She scrapped and fought and even killed Bajoran collaborators because she felt it was the right thing to do. When The Cardassians left, she put down her weapons for the same reason. Kira Nerys isn't a warrior or a killer; she's a believer. She is a woman of principle with a foundation set deep into the soil of Bajor. Her integrity rivals that of icons like Picard or Spock, and even surpasses that of her own Emissary, Benjamin Sisko.
Regardless of what the card game says.
Kira was also quite passionate in her personal life; connecting with others around her rather quickly, depending on circumstances. While it's counter-intuitive to think of someone who isn't the life of the party like Jadzia Dax, especially someone so combative, as being very sociable, Kira was. Even if you don’t believe that, at the very least she had a healthy balance between her personal life and her work.
Natasha Yar, on the other hand, has a very hard time showing her emotions. She pushes herself to be a Starfleet ideal, but her personal life suffers. Even when she's seeking companionship under the effects of an intoxicating virus, given the entirety of the Enterprise-D crew to choose from, she picks the safest, least threatening person on board, one who (of course) politely and discreetly accedes to her request that they never speak of their encounter again.
Yes, the entire crew.