[martpie]

To me, the best feature is Relay Fragments (I think Apollo has fragments too?), as each component describes the data they need: no need to do a big top-level request then pass down the data to the responsible components, everything is in one file.

It makes UI changes much much easier to deal with.

[probabletrain]

I'm a huge fan of this. Apollo doesn't have it baked in as a pattern like Relay does afaik, but I do something similar manually in Apollo, inspired by Relay.

Deleting code automatically removes its data dependencies from the root query, it's ideal.

[phist_mcgee]

I mean technically in relay you need a parent component to make the query for the child components, and pass a reference to those children. There's still a parent/child relationship that needs to be maintained.