ponderousness vs heftiness

ponderousness and heftiness both are nouns.

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

As nouns, ponderousness and heftiness are synonyms defined as:

Other synonyms of ponderousness include heft, massiveness, ponderosity.

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