That's the basic question. The documentation seems to suggest that the GraphQL API is just as capable as the REST API; but then, there are capabilities I can only find REST documents for.
Is it that the documentation just hasn't been fleshed out yet?
Solved! Go to the solution
GraphQL might miss some of the features REST API has, but usually would have alternatives, more or less equivalent. One thing for sure, any new feature is going to be part of GraphQL and most probably wont make it to the REST API.
The advice would be to embrace the GraphQL API if you are starting from scratch. Use REST API only when absolutely necessary or you don't have an alternative for the feature you are looking into using in the GraphQL.