How effective were U-boats during WWII?

[pampanito]

Originally Posted by blueparrott

Just ponder for a moment Germany in this regard...33,000 Bf 109s were produced in the space of ten years in, I belive ten different variants. And thay was only one aircraft type of many. Had Germany focused industrial capacity on the good stuff...

Yet numbers alone are not a proof of success. This huge output of Bf109s is a good example. By the end of 1942 the Bf109 was no longer a match for some Allied fighters, but the daily replacement needs of the front-line squadrons were so enormous, that Germany could simply not afford to stop or drastically reduce its Bf109 production, in favour of more advanced models. The same was true for tanks, it would have been wonderful for the Germans to equip all their armoured divisions just with Tiger and Panther, but this would imply a drastic descent of overall tank production until the factory lines were changed, so a lot of Mark IVs were still being produced in the last year of the war.
Japan faced exactly the same problem, they already had fighter planes much better than the Zero in 1944, but production could not be massively re-directed because the huge front losses had to be satisfied.

USA and the USSR had not this problem, they had enough production capacity to keep producing the needed replacements, and also for putting the more advanced weapons into line.
Some people still believe that plane for plane or tank for tank, Germany always had the upper hand, and that she was just defeated by superior numbers. That's simply not the case; in 1945 the USSR had in service tanks like the JS-1 better that anything the Panzer divisions could field, and the American P-51s were able to shot-down any plane the Luftwaffe could put in the air. And don't believe the Me-262 could have won the war by itself...