One advantage the 2004 defense has is two years of experience in the system. Few of the players in 2002 had any experience playing the 3-4 defense but now most of them have been here for two years.
Anothter advantage the 2004 defense has is the 2004 offense. The offense should be able to move the ball and score more points, taking pressure off the defense to shut out the opposing team and giving the defense more time to rest between series.
Also, the 2004 version has depth. Deloach has started 32 games. Sears started most of last year. Ioane started a few games. Those are the backups for the D-line. Peek has a year of experience on the outside, and Wong is ready to move inside if Sharper or Foreman go down. McCree started last year, and now he is backing up both safety spots. Faggins and Wright are backing up the CB spots.
The only disadvantage I see is the injury factor. The 2002 defense was extremely fortunate in only having one starter miss one game (Eric Brown). If Walker and Payne can stay healthy this defense will definitely end up being better because of the above reasons.