The advantage is React Admin is back end agnostic and you can tap into the huge React ecosystem. And with Hasura you get automatic GraphQL endpoints (Django nor Rails Active Admin do this - you have to create models first vs just a schema with Hasura) which can be used for more than just your admin backend.
Having built and maintained large Django apps for the past couple of years, I personally prefer Hasura's admin console over Django's one, not least because you don't need to write any code to get it started!
Hasura also ships with websocket support, something that Django has always struggled with.
The advantage is React Admin is back end agnostic and you can tap into the huge React ecosystem. And with Hasura you get automatic GraphQL endpoints (Django nor Rails Active Admin do this - you have to create models first vs just a schema with Hasura) which can be used for more than just your admin backend.