I don't think I have ever sat on the sofa and hugged any other doll like I have Kim, I have even dozed for hours with her. Its true that the first is always the most loved of all the dolls.
Willow is really soft and cuddly but her shoulders are slightly broader so can't get as comfortable resting my head against hers kind of thing. Rey would work, but she is usually tucked up in bed, so Kim is the main sofa cuddler and always will be.