If brm means Bedroom..... And it is going to be used just for that , I would put up greenboard ( a type of drywall used in bathrooms ) . Are you going to be doing the walls ,floor to ceiling ? And it also sounds like you are covering the ceiling too. ? Sounds kinda strange What are you going to use the room for?
I prefer a cement board backer, particularly in the bath. Local code here does not allow for drywall inside the shower area.
