Hi. It is quite simple. Criminology is focused on the psychology of the crime, abnormal behavior, and includes investigating of all circumstances surrounding the crime; while psychology deals with the human mind and its development in all spheres. Your choice should be based on what your interest is - whether the crime triggers your interest towards the psychology or you are interested of the human behavior itself, which could be absolutely unrelated to crime.
I had the same dilemma; now I am studying Criminology and I am very happy with it but I knew what exactly I am interested in. It is very important.
