I've got three slim MSD's, one YoSD, and three tinies (one only 10cm tall). They've all got their benefits and drawbacks. My MSD's are easier to make things for, and can use some items made for 18" dolls as props. Tinies are portable and cute, but such a pain to make anything for. There also seems to be less of a selection of things like wigs for them. Finding a 3-4" wig that was what I was looking for for my Illusion Spirit Anita (16cm) took forever. It probably would have been easier if I'd wanted a fantasy look for her. My YoSD is a good size for both portability and not being too hard to sew for. Their proportions are too immature for most of my characters. So I guess slim MSD is my favorite size overall. I could see myself getting an SD at some point, but not making any kind of diorama or display for the doll due to size requirements.