Drinking, drugging, and sexual activity can take place at absent-parent parties whereas they would have great difficulty occurring at your snack and soda parties. My guess is that as your son ages he will be inclined, as will his peers, to attend such unsupervised parties. It's only natural to be tempted by peer pressure.
Your dilemma is whether or not to explicitly or implicitly sanction behavior that does not conform to your value system. There is also a concern for physical safety here. I suspect your son will give you an angry response if you place party check up calls. I'm sure he will feel humiliated and embarrassed.
I don't think you should surrender your value system to please your son. I think you need to express your understanding of his wanting not to report in to you and he needs to hear your legitimate concerns in this regard. Dialogue is needed, not preaching or threatening. You certainly can ask him if he knows whether the party host's parents will be present (or if they know their house is being used for a party) and leave it at that. Whether you can live with the knowledge that you know kids are partying at another parent's house without their knowledge is a question only you can answer.
Can you come to an acceptance, albeit an uneasy one, that you will trust your son to "do the right thing" at unsupervised parties or are you unable to even entertain his presence at such events? I'm asking you more questions as opposed to giving you "the right answers" on this thorny topic to stimulate a productive parental discussion and family debate, where everyone's opinions are valued. Trust, values, guilt, safety-- all these are present in this decision-making. Good luck. Let me know what you decide.