i think this game is amazing in terms of gameplay, characters, animation, and story. Sure it's a turn based game but I like those types of game where you don't need to stare at your screen at every encounter or listening to enemy step, but there's a few reason
why I like the Japanese version more :
1. There's more chain reaction ( triple quick that gives you extra crit, ABQ Chain
2. The free 5* servants ( not every 5* btw just a few of them, but still really useful )
3. There are more 4* servants on tutorial summons
4. The drop rate is slightly higher imo ( item drop not servants )
5. And lots of free