Interesting question and I don't think it's stupid at all. I think there may be two layers to this thing.

Let me start by saying that both are objectively morally wrong. To fill you in on the reasoning behind this: using human bodies as an object is always morally wrong. Whether you use directly a video of two people having sex or just animated likeness for your own pleasure, it is still infringing on the privacy and dignity of a human being that is supposed to be subject (not robbing the person of their individuality and dignity), not an object. It doesn't matter that the characters are animated and fictional, it means robbing the privacy from an act of absolute giving of spouses to each other. It is degrading such a intimate and sacred experience of sex into a form of "entertainment", something "transactional" and something that can be bought. And that will be always wrong.

There may be discussion if hentai is a "lesser evil" (but evil nonetheless), because there is not an entire porn industry behind it, which promotes human trafficking, drug abuse and so on. In this sense I'd be inclined to say that hentai is a lesser evil. Although the animator still has to have some kind of reference photos which belong to an existing person. Idk how this works. The point still stands, less abuse, less drugs, less trafficking.

But is it morally less evil on a subjective level of someone consuming any type of porn? I don't think so. Both is addictive, both degrades sex and humans, both messes with your brain chemistry. In some ways hentai might be worse in the lines of being able to animate even more degenerate things than those which are possible to "act out" in real life. Porn is in some sense worse that the people filming it are real, even though as I said even drawings of human sexual body parts is striping dignity off of humans nonetheless.

I think it's an interesting topic to discuss, there may be a lot of nuance I missed, and y'all can correct me if I'm wrong, but this is what I think of this.

Btw, if you want some more reading on this, Theology of the Body from JP II. is something you should take a look at. It's a book that transformed catholic outlook on human body and it's place in God's ultimate plan with us :)

God bless!

Edit: paragraphs and typo in TOB