a good deal vs lots

a good deal is not a noun while lots is a noun.

Word	Noun	Adjective	Verb	Adverb
a good deal	No	No	No	Yes
lots	Yes	No	No	Yes

As adverbs, a good deal and lots are synonyms defined as:

Other synonyms of a good deal include a great deal, a lot.

a good deal (noun)	lots (noun)
	a large number or amount

a good deal (adverb)	lots (adverb)
to a very great degree or extent	to a very great degree or extent