big enchilada vs big deal

big enchilada and big deal both are nouns.

Word	Noun	Adjective	Verb	Adverb
big enchilada	Yes	No	No	No
big deal	Yes	No	No	No

As nouns, big enchilada and big deal are synonyms defined as:

Other synonyms of big enchilada include big cheese, big fish, big gun, big shot, big wheel, head honcho.

big enchilada (noun)	big deal (noun)
an important influential person	anything of great importance or consequence
	an important influential person