I don't think that you can really contrast these two -- they are not trying to explain the same thing.
Cognitive psychology is trying to explain all human behavior. It argues that people's behavior is tied to the ways in which they perceive the world.
Abnormal psychology deals with trying to figure out why people behave in deviant ways -- not with all human behavior. So there can be cognitive approaches to abnormal behavior that would focus on the negative ways in which people perceive the world. At the same time, another psychologist could focus more on the physical and chemical causes of abnormal behavior.
So cognitive psychology and abnormal psychology are not rival schools of thought.