If I had the choice between the two, I'd vote for Bioware (but that's just wishful thinking...)
I just played K1 again recently and I was amazed at the sense of detail in the textures, the dialogues, the storyline, etc in comparison to K2. Sure TSL has more items, a better upgrade and feedback system but almost everything is re-used from Kotor, even the armors which are for the vast majority, just reskins from K1. Sometimes the placeables have been reused in some weird ways too: why would the mandalorians plant Rakatan flags all around their camp???
I was just thinking about the city areas: Taris/Manaan vs and Nar Shadaa and Onderon. Well there is no comparison: Taris and Manaan are much bigger, the artwork much more detailed and there is a lot more to do in quantity and variety. In K1, there was also all that people walking in the streets, while in Kotor 2, Nar Shadaa was almost completely empty and the npcs didn't even walk but just stand in place.
You also had much more freedom in your movements in K1. In K2, you are constantly put in control pf party members you don't chose, which limits the possible interaction with your party members and increases the feeling of linearity.
The writing was also much better in K1 IMHO.
Don't get me wrong: I still think K2 was good and I had fun playing it. Obsidian had good ideas and the story began pretty well but there were too many loose ends in various aspects.
I hope that for K3, things are going to change.