KOTOR 2 had far better combat system, feat selection, and item customization.
And an actual crafting system.
And Treia is probably my favorite character out of all the RPGs I've ever played.
On the other hand, the game is unpolished, and without various mods which I haven't bothered to get it's pretty lame at some points. No assassin droid factory, and stuff like that.
Overall, I definitely like KOTOR 2 better.
But I'm currently replaying KOTOR 1, and while I miss certain feats only available in KOTOR2 (apparently KOTOR 1 doesn't seem to have Weapon Finesse, at least not on my scoundrel/rogue whatever) and the crafting system and a whole lot of stuff, I certainly enjoy playing around with blasters instead of not even bothering with them for my main character since you start as jedi.
And I really love sneak attack, because Rogue is one of my favorite D&D classes. And you couldn't really get it without prestige class as Jedi Watchman/ Sith Assassin in KOTOR 2 on your main character.
I don't really remember all the characters from KOTOR1, but I've always liked Mission and that cat girl jedi, if I remember it right. The jedi guy from Kashyyk was cool, too.
But they still, in my opinion, got nothing on the characters in KOTOR2. Treia/Creya, as I've already mentioned, is my favorite RPG character ever. She made the most awesome mentor figure, and I'd have her over that useless ***** Bastilla any day. The guy with the robot arm, forgot his name, was really cool too. I liked his character and his general background. I really can't think of any KOTOR2 characters I didn't like.
I personally find KOTOR2 a far superior game and story compared to KOTOR1. It's a lot less polished, too, and I have recently replayed it so I guess I'll stick with KOTOR1 which I haven't really bothered to beat since, like, 2003 or so.
KOTOR1 definitely gets cool points for letting me play through a significant part of the game as a streetsmart fast-talking scoundrel with 2 blasters and complete amoral personality as opposed to a streetsmart fast-talking jedi with a sword and complete amoral personality. Yay.
I love sneak attack. The moment I get my jedi prestige class in KOTOR1, I'll just pick up Stasis and abuse the hell out of Sneak Attack.
And Kreia's philosophy on force and everything is simply awesome. I so totally agree with her.