Well a regular http API is going to be better for caching. Right now I'm only aware of one product that supports caching in graphql but there are hundreds of thousands of CDN nodes around the world that will cache the result of 'GET /product/5'

HTTP2 is great if you have independent requests and want to avoid head of line blocking. I'm not aware of any sort of streaming/partial result capabilities for graphql.

Graphql is great if you want to give a trusted client a richer API and/or if your infrastructure has good ways of handling abusive API users.