The top is completely interchangeable 97-02 and 03-06. The 03-06 frame tubbing is slightly larger in diameter, but not by much. Otherwise they are the exact same, including the header bar.
The rollbar brackets are the only thing that is different between the years. The 03-06 brackets are extended rearward a little more that the 97-02. That was to accomodate the thicker rollbar padding. They make the top fit tighter on all years.
The Black Diamond is a much nicer material than the Black Denim. Not only is the color nicer, but the Diamond material is thicker than the Denim (comparing both as sailcloth material).
Here are some side by side comparisons of the 'Diamond' vs 'Denim' colors (both Bestop Sailcloth material). Diamond on the left.