Key benefits: easier data model to deal with, integrated migrations, using EdgeQL (not SQL) to write advanced queries and expose them as GraphQL views. In the future we'll have integrated access control layer, but that's a subject for another great blog post :)
The reference page has some details [1]. Our goal is to match and exceed the experience of managing the migrations with a high-level ORM like Django. This is one of the reasons behind the SDL/DDL duality. EdgeDB has to grow some tooling around it before we get to that point, though.