serious-mindedness vs seriousness

serious-mindedness and seriousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
serious-mindedness	Yes	No	No	No
seriousness	Yes	No	No	No

As nouns, serious-mindedness and seriousness are synonyms defined as:

Other synonyms of serious-mindedness include earnestness, sincerity.

serious-mindedness (noun)	seriousness (noun)
the trait of being serious	the trait of being serious
	the quality of arousing fear or distress
	an earnest and sincere feeling