portrait painter vs portraitist

portrait painter and portraitist both are nouns.

Word	Noun	Adjective	Verb	Adverb
portrait painter	Yes	No	No	No
portraitist	Yes	No	No	No

As nouns, portrait painter and portraitist are synonyms defined as:

Other synonyms of portrait painter include limner, portrayer.

portrait painter (noun)	portraitist (noun)
a painter or drawer of portraits	a painter or drawer of portraits