The graphics are pretty great. The real-world locations look really nice. The digital locations look nice enough, too, but most of what you end up exploring prior to the second half of the game are these kind of generic-looking cyber spaces. They're nice enough looking, and the colors are easy on the eyes, but they aren't exactly interesting for the most part.
All the Digimon models look really good, too. There are about 240 to collect with the preorder-bonus DLC, slightly less without it. It makes me feel like I'm playing in the anime, running around with my favorite digital monsters. I really didn't like the designs of the playable characters, though. I just found them to be yellow-and-black eyesores, though I did like the male's design better than the female's.
The battles are probably the best part. It's designed after the battles from previous Digimon Story games, but a little more streamlined. Each Digimon has a type: virus, data, vaccine, or free. Along with this, they can be one of several elements. Their moves also have elements. Each type and element is strong or weak against another.
By combining types and elements, you can do from 0.5x damage with an attack if the Digimon's type is weak against the other all the way up to 3.0x damage if the type and element of the attack are effective against that of the opponent.
It sounds a little difficult, but this was circumvented in a nice way. When you select an attack, you then get to select which opponent to attack. The selection graphic will be blue if the attack won't be very effective, white if it will do neutral damage, and red if it will do more damage than normal. It's really helpful to have this, and makes memorization less necessary and it more accessible overall.
You can also set the difficulty of the battles to normal or hard, and this can be changed at any time under the in-game options.
There are coliseums for both online and offline play, and mirror dungeons of previous areas you've gone through for re-exploring and battling wild Digimon.
For a little side quest, there are medals you can collect featuring different Digimon on them. There are 500 medals you can collect. You can find them in gashapon machines around the different real-world locations, from defeating Digimon in battle, lying on the ground, from quests, and from certain NPCs. It's not really important to the main game, but it's a fun little distraction and it's nice to see all the different pictures of the featured Digimon.
The story is interesting, but the pacing is pretty awful. I felt like the first half of the game was trying to be more story driven, and the second half more game-play driven. This just made the first half of the game a horrible slog to get through, though, because the characters arnen't all that interesting at the start, there aren't many areas unlocked, and the areas that are don't have very strong or exciting Digimon in them. So at the beginning, you'll end up seeing a lot of the same stuff over and over.
The game is played out in chapters, and there are twenty in the game. The first ten take about 40 hours to get through, and the second ten take between another 20 and 40 to finish.
The pacing during the first ten chapters just feels so slow. It took me three different tries to get through the first half just because I found it so hard to get through the story.
Once it hits chapter ten, though, things improve quite a bit. The characters have grown and changed quite a bit, the story speeds up a lot, and you've unlocked a lot more areas to explore.
The only thing that doesn't really improve are the boss battles. There aren't very many of them until towards the second half of the game, but they're still a pain. You'll be going through an area with no problem, easily defeating all the wild Digimon, and then suddenly come across the boss battle at the end of the area. You better hope you've saved recently, because I found in most instances that these were able to quickly take down all of my Digimon. This leads to several hours of grinding before heading back to the boss, and sometimes turning the difficulty down to normal to make it even possible to win.
All in all, I found this a pretty fun game. The first half is pretty slow, but if you can get through that, it really becomes a lot more fun. It looks nice on both the Vita and the PS4.