effortfulness vs difficultness

effortfulness and difficultness both are nouns.

Word	Noun	Adjective	Verb	Adverb
effortfulness	Yes	No	No	No
difficultness	Yes	No	No	No

As nouns, difficultness is a hypernym of effortfulness; that is, difficultness is a word with a broader meaning than effortfulness:

effortfulness: the quality of requiring deliberate effort
difficultness: the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result

Other hypernyms of effortfulness include difficulty.

effortfulness (noun)	difficultness (noun)
the quality of requiring deliberate effort	the quality of being almost beyond one's ability to deal with and requiring a great effort to achieve a positive result