Short-throw projectors can be mounted close to the screen, which suits smaller rooms where a standard projector would need more distance to fill the image. Standard-throw units are often brighter for the price if space allows. Room depth is usually the deciding factor between the two.
Ambient light from windows or overhead fixtures can wash out a projected image if brightness is not matched to the room. Blackout curtains or dimmable lighting make a noticeable difference in image quality. A brighter projector is not always necessary if the room can be darkened instead.