Saturn version pros:
Better graphics.
PS1 pros:
Better looking movies.
Additional movies.
1 extra boss.
From the back of the US manual:
"The major change was in making the game harder than the Japanese release. We accomplished this in two ways. First, the cost of weapons was increased and the monsters made more damaging. Second, the parasites were made to use a bit of spirit power when they were used, which made it necessary for the player to replenish this power. We accomplished this by adding a "spirit stealing" power feature where the player could "steal" spirit power from enemies. In the Japanese version, the player merely reduced the enemy spirit power if the attributes were the same.
Another change for the better was that the original had "Now Loading" screens between levels, and we added screens that were a bit more fun to look at.
The font of the in-game text was changed to something more computer-like and dual shock support added.
The title screen was fairly radically changed, with the "Options" and "Status" items being added. "Status" was added so players could track their progress in finishing all the branches of the game. Ones that do might get a nice surprise that is also exclusive to the US release!
Dual Memory card support added.
The ending credits roll (not closing animation) was made interactive, and of course the song was re-recorded into English.
All the animations were re-mastered and re-compressed to look better than any release of the Japanese game.
And finally, last but not least, the Lunar 2 preview movie was added to the disc."
Anyways, this is a really fantastic game, one of my favorites on the PS1 even if WD butchered it. Essentially the weirdest change WD did is made it near impossible to max out a weapon's power and then have the weapon's power go down if you use it too much (??? why would they do that). This forces the player to just stick with a single weapon the whole game to power it up instead of trying the others.
Now the last time I played this was in 2006, but at that time I also really enjoyed the story and dialogue between characters. Treasure games really have the best stories.