theoretician vs theorizer

theoretician and theorizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
theoretician	Yes	No	No	No
theorizer	Yes	No	No	No

As nouns, theoretician and theorizer are synonyms defined as:

theoretician and theorizer: someone who theorizes (especially in science or art)

Other synonyms of theoretician include idealogue, theoriser, theorist.

theoretician (noun)	theorizer (noun)
someone who theorizes (especially in science or art)	someone who theorizes (especially in science or art)