The extended storyline isn't really an argument to choose the PS3 version over the Wii version since it feels so... tackled on (it is even a separate game mode in the menu) aside from making a certain character (who leaves for plot relevant reason for most of the main arc) playable for more time and confirming a pairing that was hinted anyways in the Wii version FMV ending cutscene. I mean really, an additional dungeon with the final boss battle plot devices from the main arc repeated all over again? It's nowhere near the Vesperia PS3 additions, maybe 1/8th of the main arc Wii additions.
I'd rather choose the PS3 version since it improves some design choices (EXP!), and ... for the DLC costumes maybe?
But the Wii game (the bugfixed version, that is) is a beast in its own right. It's one of the best games in the Wii library, that's for sure.