BioWare - BG, BG2, Kotor were pleasurable experiences, BG2 first play through was the highlight of my Crpg enjoyment. Subsequent playthroughs have diminished my enjoyment somewhat, but I was unable to stop playing that game when it was released. NWN and it's expansions were terrible, have not played any of their other games.
Bethesda - Played FO3 and Morrowind and they were terrible the less said the better.
BioWare > Bethesda in a landslide victory.