I think the big difference between the stuff and Civil War era buck and ball is that buck and ball actually worked. We know that to be a fact from the historical record. This stuff? Who knows.
Another big difference is that buck and ball would have been relatively cheap, while this stuff is frighteningly expensive.
The biggest drawback to buck and ball is its limited range compared to a rifled musket.
But, as the Irish Brigade proved at the Sunken Road at Antietam, if they could get into effective range, buck and ball was absolutely devastating.
In fact, buck and ball features prominently on the monument to the 12th New Jersey Volunteer Infantry at Gettysburg. http://www.gettysburg.stonesentinels.com/NJ/12NJ.php