It's a subjective thing, comfort. I've had two discectomies on my L5-S1 (2010 and a redo in 2014). I sleep at home and on vacation with an extra pillow under my knees which has helped tremendously (and when I lay on my side, the pillow goes between my knees). A bed that is too firm is preferable to too soft (too soft will kill me) but I've found the beds at both DVC resorts (and BWV) to work great.
Now the guest bed at my parents house? Ooof...that's like laying on a bed of nails lol!