Defo Japanese artwork.
I prefer Japanese artwork mostly. The artworks that I like more in English are mostly because of one of my favorite Pokemon being front and center on them; love the D&P base Dialga pack, EX Sandstorm Zangoose pack. On the flip side, some of the vintage promo packs from Japan are amazing.
My brain says Japanese. My heart says English.
Japanese is more artistic and seems to tell a story whereas English isn’t bad per se but more basic.
Japanese and it’s not close. The only western packs I like more are Team Rocket because that black looks gooooood. Otherwise, Western packs are b o r i n g
Probably in the minority here, but definitely English. The Japanese artworks are way too busy. The English variety is much cleaner and generally has better composition.
I say this strictly regarding the older wotc sets. As far as modern stuff, idk