Of course I know Hitomi is a rarity. I think girls with bigger boobs who are chunky are a lot more easier to find in Europe (especially the UK) and the USA, not the American porn stars who are ultra thin but also have the big junk. I'm wondering if the same is for Japan/China in terms of the easier to find chunkier girls.
With regard to both actual body type and tastes in body type there are enough noticeable difference between Japanese and Chinese. And also the last few decades there have been rapid evolution.
Mainly there's a lot more genetic diversity in Chinese than in Japanese. So while the average measurements (just for argument's sake) may be comparable, you can find more tall, or short or fat or thin people in 1000 Chinese than in 1000 Japanese.
Another factor is wealth and diet-type (as CG said). I grew up in Hong Kong and there's a very noticeable increase in average height and weight (and breast size) in the generation(s) right after mine. And probably the war-time generation might say the same thing about mine. The same effect should have happened a generation (or a half) earlier in Japan and a couple generations later in Mainland China. The effect is most pronounced in mainland China as China went from starving to obese within a single lifetime.
That's based on economy only. If you actually take a close look at Japanese. The increase in wealth post War did not really affecting their body size much. The change seems to be subtle and late. JAV breast size becomes noticeably bigger only in last 5 years. One factor (problem?) is that Japanese traditional culture prefer androgynous body type. Big muscular men are seen as brutes and shapely women are seen as cheap. So while the traditional Chinese dress (qipao) covers as much skin as Japanese kimono, qipao highlights the curves of a woman while kimono suppresses them. Even in 2015 a survey still shows a huge percentage of Japanese men prefer A-cup breasts. I don't have any comparable survey for Chinese, but take a random guess I'd say the number of Chinese men who most prefer A- and B-cups would be under 10%.
While I procrastinate on this reply I paid more attention to body types on the street and estimate their measurement, cup size and BMI, quite ignoring if they are attractive or not. I will now both confirm some stereotypes and debunk some myths:
(1) Asians/Chinese are shorter, slimmer, with smaller boobs and butts than whites and blacks. TRUE
(1A) Asians/Chinese women develop bigger breasts later in their life than whites (and perhaps blacks). TRUE
(2) It's rare to find Asians/Chinese women who are tall, shapely, fat, with large boobs and/or large butts. FALSE
Yes, on average Chinese are smaller (both overall and various body parts). Especially compared to suburban Americans (where I lived for 7 years), the difference is huge.
OTOH, as far as the purposes we are discussing here, we are quite un-interested in national average. We are looking at and discussing women in a narrow context, as porn performer, idols, girlfriends, sex partners and wives. So there's a selection process going on anyway. What matter isn't on average or if you randomly pick a woman how big she is. What matters is if you desire a certain body type how good a chance you will success. And my observation is that there's no meaningful difference between Chinese, whites and blacks. If you desire a Chinese with a big butts, yes it's noticeably less common than amongst blacks but still easy enough to encounter. If you want a Chinese with big boobs you will find them. You might face a problem of competition as there are a lot of men who desire the limited "supply" but it's wrong to say it's a rarity.
(but it's truly rare to find a busty teenager in Chinese. Chines girls seem to develop late. You almost never see a high school girl with big boobs. College students, a few. But for women of age and especially MILF, D-cup tits are not that rare. Which maybe disappointing for many people, especially for Chinese men. )
This summer I am most delighted by a new trend in hot pants. It's almost a daily happening that I spot a woman with the ass cheeks are hanging out. Which reminds me last summer I follow a girl for 5 blocks in a major US city oogling her fantastic fit ass peeking from underneath her daisy dukes. It was such a delight, as if I were 15 years old again. And the fashion seems to have spread to Asia. Now to be honest, the "ass cheeks hanging" effect is a combination of two factors: (1) the shortness of the shorts, (2) the bulk and droopiness of the ass. So while I'm constantly on the look out for hanging cheeks, sometimes the glimpse I caught is not erection-friendly. The wonderful thing about hot pants, especially the not-tight-fitting variety is that swimsuits and tight hot pants doesn't leave any "wiggle" room. What you see is what you get. But a good pair of hot pants leave a little space some possibility for you eyesight to penetrate deeper inside, and it doesn't hold the buttocks in some fixed shape, the buttocks can breath and move and wiggle and jiggle. It's honest, it's just hanging out, chill'n. All that meat, no hiding or shaping or deceiving.
So it's with the studied investigation of many a butt cheeks that I debunk the big-ass-is-rare-in-Asians myth.