For those who have not played the original
Persona 3 on the PS2, specifically Persona 3: FES(P3:FES), I recommend getting that version of the game. It's really the "complete" version of P3, including an epilogue to the original story, which is missing in the portable version.
The biggest difference, to me, is that the sense of immersion of the PS2 Persona 3 is watered down in the portable version. In P3:FES, when you're out and about in the overworld, exploring Iwatodai, Paulownia Mall and Gekkoukan High, you are always in control of your character, in the way that you move him with the analogue stick. Not so much in Persona 3 Portable. Instead of moving around your character, you are moving a pink or blue circle, depending on your gender. You could also move the camera when exploring in the PS2 versions, but in P3P you go around the city and click on people on a (very good-looking) static image.
You do control your character while in Tartarus in P3P. Which is a big relief.
Another difference, is that the anime cutscenes, which were gorgeous on the PS2, have seemingly been removed from P3P. Replaced with in game graphics(which look pretty good too.)
HOWEVER. Now that that's over and done with it, let's get on to the goodness of P3P. For those who indeed played the original, I still wholeheartedly recommend this game. In the PS2 versions, you could only play the game as a guy. And the story translates well onto the PSP. The voice acting is still there, the social links are the same and the set-pieces are the same.
But, Atlus have added something so simple, that in a lot of games it's simply there to be there as an option. You can play as a girl in P3P.
Now, before I get excited about playing as a girl, let me tell you that this makes a massive difference in the Persona world. Everybody talks to you differently, you have different people representing different social links and a tonne of new lines have been recorded just for the female perspective. Shoji Meguro(the composer) also made a bunch of new songs just for the female side. A new battle theme, a new school theme, a new overworld theme, you get the idea.
Now the original Persona 3 is, generally, a serious game. P3P doesn't lose any of that, but with the female perspective, I think they had a bit of fun rewriting everything. The conversations feel more light-hearted, your own selection of replies seem to have more variety( a problem I had with the originals) and even the new songs just feel more fun.
Those were the changes for the female perspective, but there were also some general additions to the game. P3P borrows quite a bit, in terms of gameplay, from
Persona 4. Shortcuts to other areas have been added via the square button. You now have control over everyone in your team while in battle. You can access everybodys stats via that stats menu, no need to go ask Mitsuru or Fuuka. You can also change their equipment whenever you want, you don't need to ask them anymore.
Navigation is overall, faster in P3P, in terms of menus and exploring the world.
Load times are quick and snappy, especially with the data install(258 MB).
Persona 3 has garnered a reputation for being one the best JRPS in recent years, and rightly so. This game will stick with you for a very long time.
Buy it, it's absolutely worth it. It also comes with a nice little artbook(contains spoilers though.) and a poster, which is nice.