REST vs GraphQL: which API style should I use for a new project?

Default to REST. It's simpler to build, cache, debug, and every tool on earth understands it. You can be productive in an afternoon. GraphQL earns its complexity in two specific situations: (1) many different clients (web, mobile, partners) need different shapes of the same data, and (2) your screens aggregate data from many resources and over-fetching is a real, measured problem — not a hypothetical one. If you're a solo dev or small team building a typical app, GraphQL mostly adds a schema layer, resolver plumbing and caching headaches you don't need yet. The teams I know that adopted it happily all did it after hitting REST's limits, not before.