Research assistant vs research credit

I have been involved in research in a lab at my university for a year. I first got the position through an organization run by the university in order to match premed students with research opportunities. These positions as a student volunteer in research typically last a year. However, I decided to stay on the team and continue my work with the option of either becoming a part time employee of the lab as a Research Assistant, or counting this research as a self created lab course for credit. I am unsure of which to choose, and whether continuing my research as a science credit would disqualify it as falling under the “research” category of my medical school applications.