most valuable player vs MVP

most valuable player and MVP both are nouns.

Word	Noun	Adjective	Verb	Adverb
most valuable player	Yes	No	No	No
MVP	Yes	No	No	No

As nouns, most valuable player and MVP are synonyms defined as:

most valuable player and MVP: the player judged to be the most important to the sport

most valuable player (noun)	MVP (noun)
the player judged to be the most important to the sport	the player judged to be the most important to the sport