How about you start with your general argument for the scientific method of psychology over the other one?
Somehow I sensed I would have to before anyone else
Basically, I think that psychoanalysis has too many holes to be considered as an adequate way to make conclussions on human behavior. Freud's ideas were based out of his own subjective interpretation of several pathological cases he had treated himself, yet, there is no proof of anything he ever said, his ideas are accepted because for some it "makes sense".
Personally, I like to side with the people who prove or disprove what they say, I don't particularly feel that the behaviorist theory is "completely right" about everything, but it is one of the theories that has described human behavior in the most accurate way, they prove what they say through empyrical contrast, they make theories and base their knowledge on what can be proven or disproven, not on what someone can say and how smart he can sound while saying it.