more and more vs what is more

more and more

adv

  • Progressively more. 

  • Indicates that the statement is becoming progressively more true. 

  • In a manner that progressively increases. 

det

  • Increasingly more; a growing number of; a growing quantity of. 

what is more

adv

  • furthermore, or in addition, moreover. 

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