Anecdote: someone on another forum used to work for an American museum that has a preserved WW2 US submarine. One time, he and his boss were asked by another museum to come and give advice on renovating and preserving a German U-boat they'd acquired - so he got the opportunity to compare the two in close-up.
The pressure hull of the American submarine was basically a metal cylinder; crude but functional. The U-boat's pressure hull had sleek, moulded ends that were streamlined and high-tech... but if you looked closely, you'd notice that the two halves of the German pressure hull were misaligned and badly welded. You can't blame that on lack of materials; only on shoddy and over-hasty manufacture.
On paper, that U-boat almost certainly would have seemed to have better performance than the US sub because of its advanced design - but if the German crew had ever tried to take their submarine to its maximum depth, those faults in the pressure hull would have caused it to fail catastrophically and kill them all.