uncheerfulness vs cheerlessness

uncheerfulness and cheerlessness both are nouns.

Word	Noun	Adjective	Verb	Adverb
uncheerfulness	Yes	No	No	No
cheerlessness	Yes	No	No	No

As nouns, uncheerfulness and cheerlessness are synonyms defined as:

uncheerfulness and cheerlessness: a feeling of dreary or pessimistic sadness

uncheerfulness (noun)	cheerlessness (noun)
not conducive to cheer or good spirits	a feeling of dreary or pessimistic sadness
a feeling of dreary or pessimistic sadness