I think JAV does have more beautiful and real women overall, but most of the difference that Jonofthedead sees is probably in the presentation. JAV does have a particular style, they pretend to be documentaries, everything is "real", so they try to present the women in a more naturalistic way. Obvious breast implants kind of goes against all that. And I feel the "realness" of JAV makes amateur porn kind of redundant as well. I feel no desire to watch amateurs after watching JAV.
Maybe there are different standards of beauty in Japan compared to the USA too. An actress in the US porn indutry can increase sales by getting breast implants. Could a JAV actress increase sales of her movies the same way? Does she even need to? Probably not. Cuteness is still celebrated in Japan. Flat-chested girls are still important in JAV.
JAV are selling more "realities" compare to western porn, less fake boobs, a lot of small and limp dicks, and reasonable sex duration
and for fake boobs, its not only in porn but in modern culture, most females in most asian countries feel doesn't need to upgrade their boobs, what they want is to change their face (nose, lip, chick, eye lit, ecc)
and majority of the asian guys in east and south east asia think B cup is already big enough, we can see from most asian sex icons, they are slim with small to medium size boobs
the conclusion (I've posted many times in this forum) : western porn mindset doesn't apply in JAV and vice versa