Are Japanese Pokémon cards worth more?
Usually not: for the same card, the English version is often worth more to collectors in the US and Europe. But there are big exceptions.
Why Japanese Pokémon cards are often cheaper
Japanese sets cost less at retail and are widely available in Japan, so more copies of each card reach the market. Most Western collectors also collect in their own language, which keeps demand for English cards higher.
When Japanese cards are worth more
Cards that were only released in Japan, such as many promos, tournament prizes and Japan-exclusive sets, can be worth far more than any English card because there is no English version. The most famous example is the Pikachu Illustrator promo, the most valuable Pokémon card ever sold.
Some sets also came out in Japan first or only, which makes their Japanese cards the original prints.
Quality and grading
Japanese cards are known for consistent print quality and centering, so they often grade well. That can make a Japanese PSA 10 easier to get, which also means smaller premiums for perfect grades.
See also: most valuable Pokémon cards · price guides by set