If you are building a simple JSON API with no need for templating engines or websockets, Apollo and GraphQL give you more neat features out of the box. The key benefit of GraphQL is a structured description of all the methods your API supports, so GraphQL clients can easily see what functionality they can access and what parameters to pass in.
Figuring out exactly what endpoints an Express app supports can be tricky. And even if you have good docs for your API endpoints, it is even harder to get your API endpoint structure into VS Code. GraphQL makes that much easier.