I have never heard of a Hakko China factory. Their most recent factory is in Malaysia. Even the cheapest nastiest Hakko Red is made in Japan.
The clones are alarmingly identical until you look at the circuit board.
The original 936 was made in Japan, so it was interesting to see the new 888 move to Malaysia. The 888 cost much less than the 936 when it was introduced, and you get more accessories with it.
My experience with Weller quality is also very good. I have a WD1002 station which I am very satisfied with.
Weller is good, but their have been quality reports about low cost stations, the longevity of its heating element and tip quality; but just looking at Amazon, the differences are tiny; between the WES51 vs the 936 which are are similar products, its between 4+ stars vs 5 stars.
Since China is the current top source of electronic manufacturing, its a good testament to Hakko's reputation that copies are made of Hakko 936 and not Weller. You can of course, get better performance than the 936 by buying more costly stations, but it seems Hakko 936 technology turned out to be a good balance of heating accuracy, temperature speed, and low cost, and so the new FX 888 takes off on the 936's reputation as a general purpose workstation, rather than something for factories.
Its hard to compare irons, because you really have to compare similar models not just the entire brand, as Weller and Hakko make a lot of products. Here is one example of measurements.
http://www.oemelectronics.se/upl/doc/performance_comparison_0909_1_.pdfI don't think the difference shown really will matter in home lab use, it probably will in assembly line use in terms of errors and poor joints, doing 1000 of joints a day by hundreds of employees.