Mechanically, one of the better Warriors games in general. One of the best and most innovative decisions for the franchise is the replacement of the standard musou/super system. Now you can assign the moves that you want to four "special move" slots, each with their own meter. Other improvements to the Warriors model include an enhanced air combo system and an honestly overpowered dash system. OPPW4 also does a pretty good job with playable giant characters. Issues with some of OPPW3's mechanics have been fixed.

Of course this is a Koei Warriors game, so it still has its shortcomings. The new "Flight" characters have pretty bad move sets, and for many characters flight can often feel more like a mixed blessing or outright disadvantage than a benefit. Characters can still be pretty wildly imbalanced, and not for story/canon reasons, just from poor/neglectful design or the embarrassment of riches that benefits the popular. Some characters were certainly neglected. It felt like OPPW3 offered a bit more on replayability, while OPPW4 has you repeating the same handful of missions to grind coins/berries. The game cuts much of One Piece's story, most likely due to the reduced roster. There are some bits that just feel like lazy design or padding, like having two story missions that consist of a single fight with Crocodile (presumably just to pad the Alabasta story section and/or overall mission count.)

Mechanically, one of the better Warriors games in general. One of the best and most innovative decisions for the franchise is the replacement of the standard musou/super system. Now you can assign the moves that you want to four "special move" slots, each with their own meter. Other improvements to the Warriors model include an enhanced air combo system and an honestly overpowered dash system. OPPW4 also does a pretty good job with playable giant characters. Issues with some of OPPW3's mechanics have been fixed. Of course this is a Koei Warriors game, so it still has its shortcomings. The new "Flight" characters have pretty bad move sets, and for many characters flight can often feel more like a mixed blessing or outright disadvantage than a benefit. Characters can still be pretty wildly imbalanced, and not for story/canon reasons, just from poor/neglectful design or the embarrassment of riches that benefits the popular. Some characters were certainly neglected. It felt like OPPW3 offered a bit more on replayability, while OPPW4 has you repeating the same handful of missions to grind coins/berries. The game cuts much of One Piece's story, most likely due to the reduced roster. There are some bits that just feel like lazy design or padding, like having two story missions that consist of a single fight with Crocodile (presumably just to pad the Alabasta story section and/or overall mission count.)