The correct response based on the information given is: It would be much easier to stop the duffel bag than it would be to stop the suitcase.
This is because, according to Newton's second law of motion, an object with less mass requires less force to stop it when compared to an object with more mass, assuming they are being moved at the same speed. Thus, stopping the duffel bag (with less mass) would require less force than stopping the suitcase (with more mass).