sizeableness vs vastness

sizeableness and vastness both are nouns.

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

As nouns, sizeableness and vastness are synonyms defined as:

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

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

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