That's not exactly true. The penalties are vastly different. However, to address your other point: two 14 yo having sex, while very disturbing does not create criminal liability because they are both incapable of consenting. Moreover, there is no inherent inequality in that relationship. An 18 yo senior and a 14 yo freshman are inherently unequal. I would not say that about an 18 yo senior and a 17 year old junior, but 14 and 18 are different worlds.
The prison penalties are different but the lifetime effect of being a registered sex offender are the same.