== American Counterparts? == 

 "Like the Porpoises, the Oberons were far quieter than their American counterparts." It's not clear what "American counterparts" this unreferenced statement would be referring to. The Tang or Tench classes? They were introduced 10 years before the Oberon boats, so it doesn't seem valid to regard them as "counterparts". If it's referring to the roughly contemporary (1958 vs. 1960) Permit class, it's basically just saying that diesel-electric submarines are quieter than nuclear-propelled boats of the same era. They're also slower, cannot stay submerged indefinitely, and have shorter unrefueled range. That's why they were typically assigned different missions in Navies such as the Royal Navy that operated both types. So again, they're not really a valid "counterpart".