Read History of the Confederate States Navy by Raimondo Luraghi. Best book I ever read on the Confederate Navy. ALL aspects of it.
My opinion is that none of the raiders changed the outcome of the war. The Shenandoah's main claim to fame is her late surrender in the fall of 65 and her trip up the Thames with the Confederate Naval Ensign still flying infuriating Charles Francis Adams.
One has been left out though. The Sumter should receive honorable mention at least. She was Raphael Semmes first command and if memory serves captured about 19 vessels before she was trapped and Semmes sold her off.
The Alabama was the best known and most romantic of them all, obviously when you sink close to 60 ships, you do get the attention of your adversary. I think, however, that the ongoing controversy (never resolved to my knowldege) regarding the presence or absence of Chain armor on the Kearsage taints the end of the Alabama. It is a known fact that she was tired and loaded with damp powder. Semmes was growing weary and wanted to go to England and turn the ship over to someone else.
I think he just got his dander up when the Kearsage showed up off Cherbourg. He should not have fought her. Witnesses describe how loud and sharp the Federal powder was and how dull the Confederate powder was. The Alabama had in fact been reduced to taking her powder out on the main deck in vain attempts to dry it out in direct sunlight. But it was almost two years old.
The "Chain armor" incident is also something that has interested me for decades. It is reported by Kell (Alabama's XO) and Semmes, that they were unaware of the Chain Armor hanging from the sides of the Kearsage. It was supposedly encased by a falsw wood cover.
I think Semmes knew about it but was just too darn cocky and thought he could dispatch the Kearsage the same way he dispatched the Hatteras almost two years earlier. But to this day, the controversy exists as to whether or not Semmes knew about the chain armor. Between the armor and the weak powder, he didn't stand a chance.
Finally, at the museum in Annapolis Md. There is a piece of the stern post of the Kearsage. In it is lodged a 100 lb shell fired from the Alabama. Talk about fate!! If the powder had been new and fresh. the outcome of the battle should have been completely different. But you'all know what they say about "ifs"?
Memphis.