Haven't played the new one, but I went through the old one on the Xbox several times and from what I understand there isn't a whole lot new here aside from a couple of new martial arts styles than can be missed completely if you're not paying attention.
Jade Empire is a fairly by the numbers (structure wise) transplanting of the Knights of the Old Republic model into a new setting. Humble beginnings with hints of greatness, catastrophic change, go to first quest hub, solve everyone's problems, go to next quest hub, rinse, repeat until big bad shows his face.
The main difference Jade Empire offered is that you could control the somewhat simplistic) melee combat as opposed to KotOR's melee, which was really just a graphic representation of turn based d20 system. It doesn't make as big a difference as you think, either because KotOR hid it's underpinnings so well or because Jade Empire's AI can be easily dominated by a couple of styles.
Storywise, it's definitely competently handled in BioWare's traditionally reliable way. Moral choices are presented to the character every so often and how you choose to handle those choices shapes your characters. I played through a few times to explore both the Closed Fist and Open Palm paths and different styles presented to your character.
If you're a gear nut in RPG's, you won't like Jade Empire. Weapons you wield are determined by the styles you learn and will stay pretty much the same from the moment you learn them until the end of the game. Likewise your character's appearance will not change. (aside from the Closed Fist aura evilness/Open Palm aura of goodness that you accumulate as you progress) There is no gear in the game at all aside from the gems that you slot into your amulet.
If you haven't played it before and you like good rpg's, I recommend picking it up. It's a solid 8.5/10 game in my books. It's no Planescape: Torment or Fallout, but it'll keep you busy for a while.
