The main difference between a heated mattress pad and a heated blanket, is that mattress pads stay in one place. A person places the pad on top of the mattress and can cover it with a sheet, whereas blankets go on top of a person and move around.
Therefore, heated blankets may suit those who want to travel around with it or move it from one room to another. A heated mattress pad may be best for individuals who want to purchase a heated item simply for their bed.