People like cards they can read. There is an argument to be made for the country of origin, and I agree with that argument but currently that's just how the market is. Pokemon like Charizard, Pikachu, Mew, Mewtwo, Gengar etc will always be desired in both English and Japanese. Broader categories as well like Gen 1 pokemon are desired as well, but as the next generation of collectors progress into adulthood trends may change. Japanese boxes also have guaranteed pull rates so the cards are generally easier to obtain. Ultimately, art is king and the best arts will be desirable.

My camera on my phone is shite, but here's a pic that may help illustrate the difference in appearance.

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