I think KOTOR II's end dungeon was more interesing. KOTOR's may have been more functional, but it was also dull as dishwater. Easily the worst part of the game. KOTOR II's ending, abrupt as it was, still served as the culmination of a lot of the game's themes, and ties up some of the more interesting plot threads. If I recall, it's where Kreia really starts being honest about how she views the Force.
And besides, Scion's breakdown is fucking phenomenal if you play as a female character. Easily one of my favourite Star Wars villains, and they wrote him so well at the ending.