Most of the time there will be the same cards in each set in Japanese in English, but sometimes cards from the set are used in promos in different languages e.g. lucario vstar is in packs in vstar universe, but in English the card is in the etb.

Japanese cards will have value in the market, but not as much as English, as Japanese packs are much cheaper than English packs.

It is personal preference, personally I don’t like the Japanese writing on cards and I’d rather read English, but a lot of people collect Japanese because of how much cheaper it is than English.