A friend of mine summed it up a long time ago, from his perspective: "Here at least they TRY." Try what? Try to be pretty, sexy, feminine. I haven't been back to the West in so long I don't even know what Lao Wai Nu Ren look like anymore, hardly, unless I see them on TV or on holiday so am not startled by how slim the Chinese girls are in comparison. Reports from back in the West are a bid dire however, and I think I could easily be dwarfed and only be eligible to respective "featherweight" bouts.
So, yeah, the "girls" here are more feminine in appearance and behavior, and buy into the whole idea of it, try to be cutesy forever and like that. I can see why that would appeal to lots of guys. The tide of feminism and gender politics hasn't hit the short here yet, not really, and it's a bit like traveling back in time. This is probably good for the guys ('cause all the cards are stacked in their favor), but not the ladies, who have to try so hard to be sexy and it seems like even compete with hookers for their man's attention.
I'm just guessing it's that more than the purely biological stuff (except in Escaped Lunatic's case, in which he's absolutely smitten with everything about Chinese ladies, even the one's that win power lifting competitions in the Olympics or sport mustaches). That also connects with the stuff guys say about the attitudes of Western women.
My take on this, one one level, is that people can be attracted to whomever they want, and there's nothing wrong with liking a feminine "girl", but us guys might keep in mind that the reason the "girls" are so feminine has a lot to do with a patriarchal society in full swing and women occupying a subordinate, often subservient, and otherwise compromised position.