The Diesel-Electric (or D-E) boats do have one very big advangage over a
nuclear submarine such as the
Akula,
688 class, or the
Ohio class. Stealth is the main advantage of any
submarine and the D-E boats are inherently quieter when submerged (with the possible exception of the new
Seawolf class
SSN). SSN (Submersable Ship, Nuclear) boats are powered by nuclear reactors. The problem is that the reactor must be constantly cooled to prevent an
overload and thus a reactor
scram. This means that the coolant pumps must be running all the time, even if nothing else on the boat is turned on (such as ventilation).
The SS (Submersable Ship) boats run on electic motors when submereged. When they don't want to be heard they simply stop and "make like a hole in the water." Since the SS boats don't have coolant pumps to run they can go completely silent.
In short engagements the SS boat has an advantage over the SSN boats, however all the SSN has to do is stand off an wait until the bad guy's batteries run low or the crew starts to run out of air. When the SS comes up to snorkel her diesel engines will be heard for miles, making her an easy target.