I played the Usa version of the game on my ps3 slim.
I am not going much in depth,but I will write down some pros and cons.
You may not agree with them,but every review is a bit bias.
Pros:
- more playable characters
- bigger maps
- new mode(dream log which creates various what if battles)
- interesting side missions(treasures)
- canon story(very important to most fans of the show)
Cons:
- no much improvement on the combat system
- maps are boring
- the music they are using isnt good enough(they should use anime osts instead)
- story is clearly not the main focus since it's so poorly presented(what bothers me is that they cut canon material out and change the story which is supposed to be canon and I am not even talking about dressrosa cuz that is understandable)
- some minor characters and some important from the canon story are removed all together and replaced by random fodder characters(gin - krieg first mate,cabaji - buggy the clown arc,absalom - thriller bark,enel priests - skypia,captain kid - supernova in the battle 3 captains vs marines at saobody,fishman island hordy henchmen)
- there is even bugs with the effects/animation(smoker,luffy) possibly more which I didnt see yet
- for me personally one more con is pw games graphics in general because imho a one piece game should resemble anime/manga as much as possible and that means cell shading(just look at beautifull naruto storm games),but i wont hold that against pw3
Some last words:
It is true that One Piece revolves around fighting for the most parts,but One Piece is also an adventure.
When you remove one of this two the game just feels uncomplete.
If we compare the changes from Pw1 to Pw2 and Pw2 to Pw3 we can see that the developers are just doing a money grab because there is not that much improvement that pw3 offers that would be worth spending on if you already have One Piece Pirate Warriors 2.
There might be a bit more characters and a different story,but the combat stays pretty much the same and it's going to get boring pretty fast.
Off course fans of One Piece will get this game anyway,but not cuz it's good but cuz it's One Piece game.
I will finish with this : WE NEED A GOOD ONE PIECE GAME - AN ADVENTURE ACTION ONE PIECE GAME.
A game that will show us the beautifull one piece world and the awesome battles straw hats have.