I had the PS2 version, and once I had a PS3, I got the PS3 version and the sequel. The sequel was the first big video game letdown i experienced, and I'd have to argue that the original on the PS2 was better than the PS3.
First, The cutscenes actually changed to show your character in the outfit&saber color of your choice, the force dash feels faster and smoother, and I like how they cleverly masked the two different endings. Correct me if I'm wrong, but on the PS3 version you just get a "Press L1 for the Light Side or R1 for the Dark Side." With the PS2 version, you choose with actual gameplay. You see Vader and the Emperor standing at different sides of the room, and whichever one you attack first decides your ending.
Although I do wish that you had the power to choose and replay levels out of order, instead of going into new game plus and playing that unbearably slow tutorial level. And I must admit, I did overuse and abuse the VERGENCE code for unlimited force powers.