merit system vs system of rules

merit system and system of rules both are nouns.

Word	Noun	Adjective	Verb	Adverb
merit system	Yes	No	No	No
system of rules	Yes	No	No	No

As nouns, system of rules is a hypernym of merit system; that is, system of rules is a word with a broader meaning than merit system:

merit system: the system of employing and promoting civil servants on the basis of ability
system of rules: a complex of methods or rules governing behavior

Other hypernyms of merit system include system.

merit system (noun)	system of rules (noun)
the system of employing and promoting civil servants on the basis of ability	a complex of methods or rules governing behavior