prefer vs upgrade

prefer

verb
  • To be in the habit of choosing something rather than something else; to favor; to like better. 

  • To present or submit (something) to an authority (now usually in "to prefer charges"). 

upgrade

verb
  • To improve in condition or status. 

  • To improve, usually applied to technology, generally by complete replacement of one or more components 

  • To replace with something better. 

  • To improve the equipment or furnishings of or services rendered to 

  • To replace a program with a later version of itself, a version having a higher version number or marketed under a more recent product name. 

noun
  • An upward grade or slope. 

  • An improvement 

  • An improved component or replacement item, usually applied to technology 

adv
  • Up a slope or grade. 

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