marginal vs borderline

marginal is not a noun while borderline is a noun.

Word	Noun	Adjective	Verb	Adverb
marginal	No	Yes	No	No
borderline	Yes	Yes	No	No

As adjectives, marginal and borderline are synonyms defined as:

marginal (noun)	borderline (noun)
	a line that indicates a boundary

marginal (adjective)	borderline (adjective)
of questionable or minimal quality	of questionable or minimal quality
just barely adequate or within a lower limit
at or constituting a border or edge
producing at a rate that barely covers production costs