public speaker vs utterer

public speaker and utterer both are nouns.

Word	Noun	Adjective	Verb	Adverb
public speaker	Yes	No	No	No
utterer	Yes	No	No	No

As nouns, utterer is a hypernym of public speaker; that is, utterer is a word with a broader meaning than public speaker:

public speaker: a person who delivers a speech or oration
utterer: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of public speaker include speaker, talker, verbaliser, verbalizer.

public speaker (noun)	utterer (noun)
a person who delivers a speech or oration	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)
	someone who circulates forged banknotes or counterfeit coins
	an organism that can utter vocal sounds