It’s pretty obvious in the movies that Dooku was never fully corrupted by the dark side. Primarily due to the fact that his eyes were never yellow. On top of that, in AOTC during his duel on Geonosis with Anakin and Obi Wan, he tried warning them of the true reason behind the war. It seems like his being a Sith is more of a means to an end, and to prove a point to the Jedi/republic.

In the clone wars, he is portrayed as a super villain. Ruthless, killing at will, and much more corrupted by the dark side. It doesn’t really match with the rest of the vibe from the movies. It just bothers me a little bit.