To my knowledge the G 650 GS is still manufactured in Berlin, but the engine is done by Loncin in China. The current F series are all equipped with Austrian Rotax engines.
In the German press BMW firmly insists moving of the engine production to China being not a cost measure, but it has to be seen in conjunction with reaching new markets on the long run. They say the engine is produced to the same standards and specifications, indistinguishable from the Rotax product. I am not a fan of China produce, but also I have to recognize, that the ride reports by the German press confirm what BMW says, no disadvantage whatsoever known.
Here are some further readings:
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Wikipedia about the 650
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Women Riders Now review
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Ultimate Motorcycling review
I am afraid I am not much help with regards to your buying decision. I rode the 650 thumper a couple of times. While I think it is one of the most matured 650 1-cylinder bikes, on the other hand to me it is too small. I feel it rides like a bicycle. Some might love it just for that. As well I prefer having a little more power available. While it may be able riding circles around the DL650, power-wise the DL650 is a different class. If you do not need the power but you are comfortable with a bike which can make a steady 65 - 70 mph, then the G 650 GS might be worth a try. Does BMW offer test riding bikes in the US?