I feel the Type 21 is an excellent trade off with losing the deck gun. Why have it when you can do so much underwater? A true submarine not simply an under water boat.
With it's speed, homing torpedoes and depth range I feel if they had come out sooner and had a better leader than Hitler they would have dominated the waters of the Atlantic and Pacific. I would have loved to have been a captain on one of those.
http://3.bp.blogspot.com/-zX3U0lEE1s...1600/Uboot.jpg
http://chivethebrigade.files.wordpre...g?w=919&h=1374