“I recently purchased some green coffee from Maui and Kauai. The beans are much smaller than from Kona. Are the the coffees from Maui and Kauai different than the better known origin of Kona, and are they inferior?”
Coffees from each of the Hawaiian Islands have unique flavor profiles, as do many of the smaller microclimates found on each island. The same is true in every origin where specialty coffee is produced. True, there are some very good coffees grown in the Kona district, for example the 97 point “Kona Sweet” grown by Hula Daddy; however, the coffees of other islands or regions of Hawaii should never be described as universally inferior.
Each variety, method of processing and microclimate of origin develops unique flavor characteristics; for example, the Caturra or Catuai that you purchased from the Kauai Coffee Company (the primary grower on Kauai and at 4,400 acres, largest in the State, by far) will taste very different than what is possibly (because you described them as “very small”) the Mokka varietal grown at Kaanapali Coffee Farms.
Most (but not all) of the coffee grown in Kona is of the Guatemalan Typica variety but some older trees are Bourbon. Each will have differing growing conditions, soil chemistry and methods of processing, thus adding to the variances between origins and to their individual complexity. A skilled roaster will recognize the characteristics of these coffees and design a roast profile that accentuates their strengths.
You may want to check out the Hawaii Coffee Book written by my colleague Shawn Steiman on the subject. It gives a good overview of the different growing areas of our state.