ponderosity vs ponderousness

ponderosity and ponderousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
ponderosity	Yes	No	No	No
ponderousness	Yes	No	No	No

As nouns, ponderosity and ponderousness are synonyms defined as:

Other synonyms of ponderosity include heft, heftiness, massiveness.

ponderosity (noun)	ponderousness (noun)
the property of being large in mass	the property of being large in mass
	an oppressive quality that is laborious and solemn and lacks grace or fluency