underestimation vs underrating

underestimation and underrating both are nouns.

Word	Noun	Adjective	Verb	Adverb
underestimation	Yes	No	No	No
underrating	Yes	No	No	No

As nouns, underestimation and underrating are synonyms defined as:

underestimation and underrating: an estimation that is too low; an estimate that is less than the true or actual value

Other synonyms of underestimation include underestimate, underreckoning.

underestimation (noun)	underrating (noun)
an estimation that is too low; an estimate that is less than the true or actual value	an estimation that is too low; an estimate that is less than the true or actual value