There's one thing about confederate ironclad production though: like it's been mentioned before, 4 of the potentials are in the Mississippi. For some reason this has been mentioned as being an advantage. It's not. There's not much you can do with ironclads in the mississippi apart from preventing union gunboats to get in; but those ironclads won't save memphis or Corinth from capture once the ground troops get rolling. Try to take your ironclads out of the mississippi, and face the brunt of Union fire from Ft. St Philip. If the union hasn't taken the place by the time you're building ironclads, well, there's a good chance you're going to win anyways then. Building ironclads on the atlantic coast is not as appealing; union ironclads are closer, and the blockade fleet is usually thicker than in the gulf. Sure, it's annoying for the union to have a bunch of southron ironclads pop up in the atlantic coast all of a sudden, but then again they're not impossible to kill, and their production puts a strain on the southern economy anyways. That pretty much leaves Mobile, maybe Jacksonville (I forget if the place can even produce ironclads - it usually falls fairly early in the game anyways), as the best "cost/effect" tradeoff places for building ironclads.
I am not denying the efficacity of one ironclad in the Mississippi. I hate having union gunboats roaming all over the place. But if the southern ironclad stays in the mississippi (which it will unless it wants to take op. fire), it's not going to go on a rampage killing union boats and transports and gaining stars like crazy like some people mentioned here.
ps: I don't know about other union players, but I usually build at least 4 ironclads from the get-go anyways. The economy can afford it, and besides, I think they look pretty cool.
"Hard pressed on my right; my left is in retreat. My center is yielding. Impossible to maneuver. Situation excellent. I am attacking."
-Gen. Joffre, before the battle of the Marne