well, I think it should be about the same. Guts's friends were killed in front of him and his girlfriend was raped by his best friend but, he was already a adult when that happened.
However, Clare lost a mother and that happened in front of her eyes while she was only a kid. That scarrs people for life.
Honestly, I can't say who has a sadder backstory. And even tough Claymore is WAY better than Berserk, Yagi had some inspiration on Miura's work.