My opinion:
KotOR is a more consistent, rounded game. It had harder combat.
TSLs good points were very good- more complicated story, better implementation of certain feats, crafting items etc....but it's bad points were very bad (you should know what I mean). Combat was much easier.
I like them roughly equally as a result. KotOR's a good old Jedi romp, whereas TSL is harder work but equally rewarding.