collector's item vs piece de resistance

collector's item and piece de resistance both are nouns.

Word	Noun	Adjective	Verb	Adverb
collector's item	Yes	No	No	No
piece de resistance	Yes	No	No	No

As nouns, collector's item and piece de resistance are synonyms defined as:

collector's item and piece de resistance: the outstanding item (the prize piece or main exhibit) in a collection

Other synonyms of collector's item include showpiece.

collector's item (noun)	piece de resistance (noun)
the outstanding item (the prize piece or main exhibit) in a collection	the outstanding item (the prize piece or main exhibit) in a collection
	the most important dish of a meal