They are all the same. The letters after the color code (1=black, 2=blue, 3=green, etc.) merely indicates the target market. Only on rare occasions is there an actual technical difference - like on some JDM (japan domestic market) models vs export models.
The size is the same but sometimes even the Casio hompage doesn't list the right size. The difference in price - don't know. Sellers ask what they think somebody might be willing to pay and the MSRP is different in different countries: for example most of the time a G-Shock costs the same in € or US$ - which means that G-Shocks are much cheaper in the US because 1€ is worth more than 1US$.
There is no difference between these watches. A G-9100 is a G-9100.
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