It's all a matter of preference.
For me, KotOR had a more interesting PC, more interesting story, more interesting party NPCs, more fleshed out part NPCs, was more complete (far more!) and had better worlds.
KotOR II had some very cool new features (like eg. the weapon switching or random loot system), new force powers, a few new weapons (nothing important, though), alternative party NPCs for the same spot (Mira/Hanrarr and Handmaiden/Disciple), more epic battles and more Sith Lords. But all this is not important enough to give it the edge over the first game.
If I could play KotOR with the new features and force powers from KotOR II, I would be a happy man.