They were both masters in their own rights. I also think that Lugosi had a comic side that wasn't fully explored-"Mark of the Vampire" brought that out--though there are some good gags in Dracula as well-- Karloff got to be the Grinch later on. I also heard of a lost movie where Bela played a non vampire count--something like "Grand Hotel"
It was too bad that Dracula trapped him into the evil roles.