Vicar of Christ vs John Paul I

Vicar of Christ and John Paul I both are nouns.

Word	Noun	Adjective	Verb	Adverb
Vicar of Christ	Yes	No	No	No
John Paul I	Yes	No	No	No

Vicar of Christ (noun)	John Paul I (noun)
the head of the Roman Catholic Church	the first Pope to assume a double name; he reigned for only 34 days (1912-1978)