It was a different warfare, mainly because of the very different theater of operations, Atlantic versus Pacific. Americans started with much of their doctrine based in lessons learnt from the germans of WW1, adapted to their own needs. The "Fleet submarine" was called like that because it was expected to work with the fleet, as scouting unit (Thus the required high speed on surface), when Mahan's doctrine was still considered and a clash of battleships was expected. Pearl Harbor and the subsequent carrier battles changed that dramatically, and the Navy discovered the potential of Fleet subs as surface raiders, though it took a long time to allow the use of aggressive tactics, like Morton showed. In the end of the war, americans also made surface attacks at night going really close, and they operated in wolfpacks with devastating success. The difference came when the younger commanders pushed their way, tearing appart the older ones who had distinguished themselves during peace time keeping clean subs. Germans instead built an elite submarine fleet in great secrecy, with aggressive young officers from the beginning, trained in daring tactics. If you are interested in comparing the difference of philosophy, a recommended reading is the U-Boat commander's handbook
http://hnsa.org/doc/uboat/index.htm versus the official US submarine doctrine
http://www.ibiblio.org/hyperwar/USN/...oct/index.html There you will see the differences in cautiousness
In technology I would not say that germans were more advanced. True, they had the german way of building things (Allowing their subs to go deeper then their US counterparts), but ultimately americans had a much better TDC and of course the radar, something the germans only could start dreaming of towards the end of the war. Plus a heavy punch with their large numbers of torpedo tubes. Only the faulty MK14 torpedoes ruined an otherwise mighty pack :hmm:
Dress code: True the dress code was not as relaxed aboard US subs (Although pics of crewmen in underwear or without shirt are not rare, due to the heat), but overall the relation between officers and crew was way less relaxed on U-Boots.
Hope that clarifies some points