Does GraphQL have more content than REST API?

Hi everyone! I’m a quite new in GraphQL and looking for the best way to grab all information about particular DOI from DataCite, so my question is: what are the advantages of using GraphQL API over REST API, I mean in next sense - do GraphQL api contains more DOIs (I guess in the GraphQL terms it called Works) than REST API or maybe it contains more information and relations for particular DOIs? For ex: I know that GraphQL contains near 8 millions of Crossref DOIs, so I’d like to know if I should use GraphQL API to get metadata of also for such DOIs or I can get such info from the REST API as well?
I’m also wondering to know if there is a method in GraphQL to filter works by source, smth like: Identifier=“Crossref”.
I would be very grateful for your answer as well as for some links to the documentation where I can find additional info related to my questions. Thanks!