masterwork vs pièce de résistance

masterwork

noun
  • A piece of quality, indicative of having been made by a master; a masterpiece. 

  • A piece done to prove possession of skill sufficient to be ranked a master. 

pièce de résistance

noun
  • A masterpiece; the most memorable accomplishment of one’s career or lifetime. 

  • The chief dish at a dinner. 

How often have the words masterwork and pièce de résistance occurred in a corpus of books? (source: Google Ngram Viewer )