I voted for ''like them all'' !! And I do! Reason being, a variety in faces can show different character traits. Much you can do with swapping parts and customisation there
Lets face it, Playmobil does this for marketing issues: It may be that a child growing up in the digital world today is not too much drawn in just a smiling face. It works ok for us who grew up with it, and with more clearcut notions of, lets say, good and bad, but for someone to like playmobil today and be drawn to it, it needs to have more variety. Company's target groups is mainly children, so their strategies are directed towards them. And judging on variation, and how distinctive selection can work for different kids or adults, this marketing policy seems very effective!!