On the flipside, Canderous in Kotor1 holds his honor in high regard as you come to learn, and when someone challenges it he demands to go fight. Carth is all pissed off and whiny a lot of the time because of a dead family and betrayed by friends who helped kill them. Life dealt him a bad hand. Mission (the bubbly blue girl) is all happy go lucky because she's a born and raised crook, meaning that as a kid survival IS her fun time. As you talk to these three characters, you learn that Canderous has seen some things that you can only dream of at this point, Carth has gone through several of his own hells and betrayals, and Mission has been street living and stealing with a horrid family for as long as she has been alive. These are deep stories that you run into, that I just didn't really see at all in Kotor 2.
You can say that the characters in KOTOR 1 had "deep" stories because of their "angst" or whatever. But they are all personal backstories, and that's all they are. What do they really add to the main plot? How are any of the characters besides Carth, Bastila, and Canderous related to the whole Jedi Civil War/Mandalorian War ???
They're not. None of them are related nor do they give you their own opinions on anything regarding the actual storyline. You have Mission, Juhani, Jolee all talking about themselves, but never anything related to the story. They are character archetypes, characters you've seen in countless other RPGs, they are just there for the sake of having a new character and to fill a character archetype.
See in the sequel guys like G0T0, Handmaiden, Visas, heck even T3 would give you information about things you actually had to know regarding the main plot, you talk to them and you will gain knowledge of the story, the republic, the Sith, they tell you stuff that are related to the ACTUAL story.
After finishing both games I realized how ridiculously unimportant your party members are in KOTOR 1. I mean a lot of them are not really related to the story at all, they are just there to fill an archetype. The second game actually had party members who mattered and is related to the story, meaning you have to talk to your party members to get the full storyline/plot, or else things won't make sense.
Here are the characters in KOTOR 1:
Juhani - Not related to the story at all except for her little Taris backstory, but why is she even there, to fill the archetype of the badass alien chick I guess.
HK-47 - Not really important except for the sand people translation. Other than that he's not very related to the plot, isn't that important but has funny "meatbag" lines.
T3 - Completely useless and not related to the story after Taris. Fills the "R2-D2" role I guess.
Jolee - Pretty much not related to the story, doesn't really care about the Republic or anything, preserves animals, he's the "old cranky Jedi character" in the game.
Zalbarr - Just barely any relation to the story except for his one required side-plot, plus he has NO, I mean NO opinion on anything. He was the strong wookie archetype I guess.
Mission - Fills the happy sidekick archtype character, but really has absolutely nothing to do with the main plot.
So the only characters that give you any information on the history or the backstory is Canderous, Bastila and Carth, they are the only ones who drive the story and tells you stuff about the past and the Mandalorian Wars and Malak.
Now here are the KOTOR 2 characters:
Bao-Dur - This guy is the reason Malachor V blew up, he was your comrade during the Mandalorian Wars, so he follows you now to put an end to things.
Atton - Also served in the Mandalorian War, also served under the Republic and the Sith, although he didn't talk about it too much he still has relation to the plot, and his encounter with Sion towards the end makes more sense. I think he even mentioned fighting on Dxun when you land there.
Kreia- The sole reason why this whole KOTOR 2 exists. She is the plot.
Hk-47 - No longer just a droid with funny "Meatbag" one-liners, in this game he serves as the voice of Revan. Since Revan couldn't be in the game, HK-47 speaks for him in a way, if you unlock his dialogue, he has tons of information regarding Revan, his philosophies, his tatics, the Republic, the Sith, I thought he was the best and biggest improvement in the writing department from KOTOR 1 to KOTOR 2.
G0T0 - He is one of the main reasons why the Republic has gone to hell in a handbasket, it's because of this guy. But you have to unlock his dialogue to know that though, and it's pretty hard to gain influence with him. Talking to him alone will solve at least 2 or 3 plot holes in the game (which you thought were plot holes but really isn't).
Hanharr - If you go LS he would be manipulated by Kreia. DS path, he has little to do with the main plot, but still the best Wookie ever in any SW stories.
Handmaiden - She is the bodyguard of your former master, and she will tell you stuff regarding your former master, plus the secret Jedi Academy.....and also important info on another member in your party.
Visas - She has also been affected by the Mandalorian War, in a sense she survived her own war, and now she follows you.
Disciple - Works for the Republic, and follows you to get things back in order.
T3 - Unlike the first KOTOR, he saves your butt a million times, and plus he is information overload. You want to find out what happened to the Ebon Hawk, or Revan, then talk to him as much as you can. He will tell you tons of stuff.
Mandalore - The only character who I thought was a bit unnecessary, but he obviously fought in the Mandalorian Wars, had tons of history with Revan, and tells you where Revan has disappeared to.
Mira - The only party member who probably doesn't have to do with the main story.
So in KOTOR 2, only Mira had very little to do with the story.
I felt that Nihlus and Sion were *dislodged* from the whole narrative, like they were operating on a different plane of existence and had no impact whatsoever on the story. The sith assassins could easily have made their move without them and the reason for Nihlus and Sion to be there is to unseat Kreia. After that they felt like a chain on the story.
Sion's role is much more improved if you play a female Exile, there's actually a reason he's chasing you. If you're a male Exile, then yeah he's just a psycho dude.
As for Nihilus, I didn't really understand his role in the story either. Like....why is a boss in the story? I know he's the lone survivor of the Malachor V thing, but still...if they made him into an NPC which you can interact with that would be so much better. Or maybe this just went over my head.