I prefer Japanese, the quality is just so much better. Often the texture pattern on English FAs is off, which I find really annoying, plus as @xzini mentioned the level of detail in Japanese FAs is so much more.
Additionally, pulling a FA in a Japanese box is far from guaranteed, so when you get one itās really exciting. With English you kinda expect it.
While Iām an English collector through and through, Japanese full arts are honestly so much better. The quality of the textures and patterns are very outstanding, making the cards have a very dynamic and three dimensional feel to them. (Not physically, but visually) I also like the darker pigment on the Japanese full arts. I feel it offers a higher contrast on the lighter part of the cards, causing them to read and pop very nicely.
And this might be an unpopular opinion for some, but I love the look of the mega FAs! I love the variety of colors and patters and the incorporation of text. My personal favorites are M Pidgeot FA, M Rayquaza FA (Roaring Skies/Emerald Break), and M Aggron FA.