affirmer vs asserter

affirmer and asserter both are nouns.

Word	Noun	Adjective	Verb	Adverb
affirmer	Yes	No	No	No
asserter	Yes	No	No	No

As nouns, affirmer and asserter are synonyms defined as:

Other synonyms of affirmer include asseverator, avower, declarer.

affirmer (noun)	asserter (noun)
someone who claims to speak the truth	someone who claims to speak the truth