Main one is that you deliver less content if you serve JSON instead of HTTP. Pros: You don't have to rebuild a full HTML page for every new query, be it server

Main one is that you deliver less content if you serve JSON instead of HTTP. Pros: You don't have to rebuild a full HTML page for every new query, be it server-side of client-side, you don't have to serve assets for every request and client doesn't have to recall/reinterpret them, less content means it's served faster,... Cons: More strain is put on the client (virtual DOM, keeping the front-end framework in memory). Though it's negligible on most clients.