There isn't really much to debate as it is obviously a matter of taste. I mainly watch JAV these days. Sometimes American. Started out watching American in the 80's.
Western porn is uncensored and mostly in English. Those are its major advantages. Smaller advantages are specific to taste: I enjoy watching anal, and there's is far more of it in western porn. Also, more throaty BJ's.
JAV has two major advantages. First, the women are on average better looking than in western porn, and I say that as someone who does not prefer Asian women over white women, or vice versa. JAV just pays better so they can recruit more attractive actresses.
The second advantage is a big one, and it has to do with storylines. It's not just that JAV usually has them , while most western porn has gone gonzo. It's that in JAV they know how to develop a story in a way that enhances the erotic impact of the movie. They understand that the story and the sex are connected, and they know how to patiently build the story in a way that draws out the tension to where you might just explode before the sex even starts.
They can't do this in American porn, and never have been able to. The 70's American porn that is sometimes amusingly called "the golden age" of American porn, where it was all shot on film and shown in theaters, was dirt boring. Those guys in the early porn were often failed Hollywood directors who thought they could make real movies that just happened to have hardcore sex scenes in them (watch the movie "Boogie Nights" and listen to Burt Reynolds' spiel about the porn he really wants to make, for a parody of this aspiration). So the stories, though somewhat better done than the later American VHS porn, didn't add anything to make the movie any hotter.
This is why American porn went heavily into gonzo in the 90's. Because they couldn't do storylines. People would rent the VHS tape then fast forward through the dialogue to get to the sex scenes. They incorrectly concluded that all viewers wanted to see were the ultimate sex acts, instead of correctly blaming themselves for not delivering anything stimulating other than the sex.
In fairness, I should mention two things I don't like in JAV: pantyhose, and vibrators. I guess since American women largely quit wearing them in the 90's and have gone mostly bare, that is what is sexy to me. Pantyhose I think of as something my mom wore when I was a kid: not a very sexy image. And vibrators, never in American porn - I find them boring. A big dildo is cool, but a little thing that goes "bzzzz" not so much. I think Japanese culture is very techy and in into gadgets so that might be why it's a thing there.
Lastly, I will mention that a few American companies are trying to do JAV style porn. Unfortunately they are regulated to the "fetsih" arena which tends to mean the budgets are lower and the women less attractive. The best of these is primalfetish.com. They do vignettes rather than features, but they do like to draw things out with dialogue and teasing the viewer for a good while before the sex. They do hypnosis, mind control, cosplay (superheroines getting abducted and r***ing), aphrodisiacs, and lots of incest. Plus other fetishes, all of which are the types you see in JAV.