The comfyness of a chair depends very little on softness, in my opinion. It really needs to be only as soft as will not insult one’s bum bones. More important are: the height of the seat from the floor; the depth and degree of tilt of the seat from front to back; the height and angle of the back rest; and the height of the arm rests.

A wooden rocking chair with those attributes correct for you will be more comfy than the most expensive down-filled designer thingy that strains your lower back. As in so many aspects of life, it’s all about the engineering.