choice of words vs formulation

choice of words and formulation both are nouns.

Word	Noun	Adjective	Verb	Adverb
choice of words	Yes	No	No	No
formulation	Yes	No	No	No

As nouns, formulation is a hypernym of choice of words; that is, formulation is a word with a broader meaning than choice of words:

Other hypernyms of choice of words include expression.

choice of words (noun)	formulation (noun)
the manner in which something is expressed in words	inventing or contriving an idea or explanation and formulating it mentally
	the style of expressing yourself
	a substance prepared according to a formula