senior status vs seniority

senior status and seniority both are nouns.

Word	Noun	Adjective	Verb	Adverb
senior status	Yes	No	No	No
seniority	Yes	No	No	No

As nouns, senior status and seniority are synonyms defined as:

senior status and seniority: higher rank than that of others especially by reason of longer service

Other synonyms of senior status include higher rank, higher status.

senior status (noun)	seniority (noun)
higher rank than that of others especially by reason of longer service	the property of being long-lived
	higher rank than that of others especially by reason of longer service