I have to go Bioware. Every game i have played that Bioware created (Jade Empire, KOTOR, Mass Effect 1-3) i always feel a connection with the characters. I either hate, or love the characters. No in between. Bethesda on the other hand has never really had characters with much depth in my opinion, except in Fallout 3.
Bioware keeps recycling their characters though for every single series. You see Leliana, Dawn Star and Liara are the same "ingenue female heroine" as Morrigan, Silk Fox and Miranda is the same "femme fatale character".
OTOH, Bethesda's characters tend to be flat as a paper sheet with a few exceptions.