From the doc:

Comparison with express-graphql

- express-graphql works with Express and Connect, Apollo Server supports Express, Connect, Hapi, Koa and Restify.

- Compared to express-graphql, Apollo Server has a simpler interface and supports exactly one way of passing queries.

- Apollo Server separates serving GraphiQL (an in-browser IDE for exploring GraphQL) from responding to GraphQL requests.

- express-graphql contains code for parsing HTTP request bodies, Apollo Server leaves that to standard packages like body-parser.

- Apollo Server includes an OperationStore to easily manage whitelisting.

- Apollo Server is built with TypeScript.