Is it more effective to insulate the walls, or ceiling of an unheated basement?
If the ceiling of the unfinished space is the floor of the bedroom and is uninsulated, the floor of the bedroom is going to be cold. It would help a lot if that floor was insulated. There is not any real downside to insulating that floor or the unheated space. Insulation on the walls of the unheated space would help a bit, but you will see much better results if you insulate the ceiling/floor first. Doing both would be great.