in other words vs that is

in other words

adv

  • used to introduce an explanation, simplification, or clarification 

prep

  • Stated or interpreted another way; Used to introduce an explanation, simplification, or clarification. 

that is

adv

  • In other words; that is to say. Used to introduce a clarification or explanation 

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