There are many benefits, depending on your situation. If your website is expected to get a high QPS, or you have a lot of data (e.g. millions of rows) then using the datastore can be much more suitable (you don't have to deal with schema migrations or connection limits etc.)

You, of course, have to put much more thought into the model design on the datastore and your design should play to the strengths of a non-relational store but once you have that right your site will seamlessly scale.

But CloudSQL is also more suitable in many situations, there are no aggregates or joins on the datastore. You need to to pick and choose the right technology for what you are doing.

Djangae is awesome here, because you use a consistent API for both CloudSQL and the Datastore, which makes switching between the two much easier.

CloudSQL works great for django, I suppose that these attempts to port django to cloudstore are looking for the free tier that is provided. In theory you could host an app for free if it's small and uses the datastore. While with cloudSQL you'd have to spend some money