big deal vs big enchilada

big deal and big enchilada both are nouns.

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

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

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

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