As pointed out in previous post, the difficulty has been changed a little as far as the AI as well as enemy positioning. Basically the enemy doesn't appear in the same formation every time you get into a battle. The overall difficulty of the first play through on PS3 is equivalent to the Encore difficulty on the 360, so that just gives you an idea how easy it was on the 360 version on the first go.
There are actually some key cut scenes that were missing in the 360 version that made the plot line make the plot line make a little more sense (not by much).
There were 2 characters added to the game and the costumes are really just for aesthetics purposes, so you can't really say that's ALL they really added.
They added pretty much an extra dungeon that was actually quite fun that the 360 did not have and it definitely added more to the game than just a small difference, and it fit in quite well with the rest of the decor.
They took out a lot of items in the 360 version that made the game way too simple and easy to abuse.
They also fixed up the battle format so it's easier to switch between skills on the battlefield as opposed to the system they used for the 360, although I was used to that version anyways.
Overall there were quite a few subtle differences in the PS3 version than the 360 version, although most of them are not obvious, but when you play it through compared to the 360, it does feel like a completely different experience.
I definitely prefer the PS3 version over the 360 version, especially playing through both Encores already, the differences are definitely noticeable and not just all aesthetics.
Anyways, hope that was helpful and didn't really spoil anything for anybody.