The difference between Alice and Bob and Andrew and Bob is that neither Andrew nor Bob will become impregnated.

Statutory rape is very much valid rape, even if both parties are consenting! This is because, similar to in the 'drunk' cases you continually pose, if you're underage you are considered not to have enough understanding of the decision to provide informed consent.

Insinuating that one type of rape is somehow 'worse' than another is really missing the point, dude.