Never played the original Xbox version, but have always been attracted to the next gen one. Not gonna lie, it's mostly for the additional bells and whistles, like the "better" UI. Still very similar to the old gen one, but it looks sharper and more polished, the globe behind, all the effects and everything. The camera pannings especially during corner kicks, the quick settings when the play stops where you can adjust things on the fly and meanwhile you see the manager giving instructions or some other player animations.
I know it's nothing gamechanging, but it gives the game more flair. More than it already has. I kid you not, I think FIFA World Cup 2006 is the game that captured the best the atmosphere of this competition. I love the seriousness of a World Cup game that's being captured and then the explosion of joy when the music starts for the pre match presentation with the line ups and the commentators. The crowd sounds and looks alive, with confettis, balloons and everything. It really gives you the feeling that this is the World Cup, this is where you want to be.
But I might be biased, a lot. I know many regard FIFA World Cup 2010 as the best World Cup game ever (I've only played it for too little to have an opinion of it), but 2006 has a special place in my heart. It's the first World Cup of which I have memories, the best memories since we went on to win the Cup, but in general I love it as a competition. I think it captures perfectly the style of the early-mid 2000s, it's the last World Cup with great legends of this game and at the same time it's the first World Cup of players that now are legends of this game, like Messi and Cristiano Ronaldo. It's the last World Cup with that unmistakable late 90s early 2000s flair