U.S. subs had air conditioning I have read, & German did not. German boats had a straight shot from conning tower to control room which made for faster dive. U.S. boats had a more indirect route. This data is from a US sailor who was on board a German captured boat that was brought to US after war. U.S. subs could make 21 knots on surface compared to 16 knots for German boats. Both had forward & aft torpedo tubes. Which could dive deeper? which had more range? Ones of similiar size that is.