heftiness vs brawniness

heftiness and brawniness both are nouns.

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

As nouns, heftiness and brawniness are synonyms defined as:

Other synonyms of heftiness include brawn, muscle, muscularity, sinew.

heftiness (noun)	brawniness (noun)
possessing muscular strength	possessing muscular strength
the property of being large in mass