vastness vs sizeableness

vastness and sizeableness both are nouns.

Word	Noun	Adjective	Verb	Adverb
vastness	Yes	No	No	No
sizeableness	Yes	No	No	No

As nouns, vastness and sizeableness are synonyms defined as:

vastness and sizeableness: unusual largeness in size or extent or number

Other synonyms of vastness include enormousness, grandness, greatness, immenseness, immensity, wideness.

vastness (noun)	sizeableness (noun)
unusual largeness in size or extent or number	unusual largeness in size or extent or number