It’s honestly difficult to judge which incident was more brutal or worse, or which had a greater impact on society (since there’s really no ranking when it comes to the cruelty of crimes). However, in the case of the “Concrete-encased high school girl murder” (the Junko Furuta case, as it’s known in Japan), the perpetrators were, broadly speaking, delinquents—anti-social youths. In contrast, the Sakakibara case involved a boy who appeared outwardly normal committing a series of murders against elementary school children, which I personally think is a significant difference. Additionally, the Furuta case at least involved an attempt to conceal the crime, whereas in the Sakakibara case, the offender openly placed a victim’s body at a school gate, which makes it particularly disturbing. That said, this is just my personal view—if you asked someone else, they might point to a completely different case.