first choice vs optimum

first choice

noun
  • The most suitable and most optimal choice. 

  • The prime cut. 

  • The one with the highest ranking. 

optimum

noun
  • The best or most favorable condition, or the greatest amount or degree possible under specific sets of comparable circumstances. 

adj
  • The best or most advantageous; surpassing all others. 

How often have the words first choice and optimum occurred in a corpus of books? (source: Google Ngram Viewer )