Shit I just saw this and was gonna' recommend War of the Lions, I've got it myself and shit yeah it's tons better. Pretty much what moog said actually, new cutscenes, new character classes, more dungeons and an extra hidden boss, lol.
If you can find it anywhere, I'd definitely say pick it up, it plays much better than the original, lol.
I'm playing Disgaea 3 again, was gonna' play MAG and get level 60 so I can vet into another faction, but meh, just done Corpse Eaters on here so I'm gonna' grind like fuck, lol. It's great, before I did it, I had 1.7m, and weapons were like 700k each so that's not bad, but from the fights I'm getting 300k per and can finish them in 2 turns, which is like 30-60 seconds, so now I'm looking for a good sword at 4.4m, lol. It's annoying, I can have a sword that gives 1159ATK and 280HP, or 1217ATK but no HP... I can't decide!