I don't know enough about the cutting of their heads, but circumcision has been proven to have health benefits. While circumcision is painful as well, the foreskin is unnecessary and the procedure lowers the possibility of more pain later on in the child's life, whether it's due to infection or an increase in STDs. (circumcision has been proven to decrease the likelihood of getting STDs and AIDs) Cutting a baby's head open has no positive effects for the child and is sadistic and cruel and could possibly lead to infection. Any of the arguments on religious grounds are pretty much equal to one other and are subjective so I'm not going to mention that except that the covenant is mentioned in the Torah. I'm not sure what sort of scriptural basis the cutting of people's heads has in the Quran, although you can pretty much find a scriptural justification for any kind of sick and evil act if you really wanted to.