Both are API-first with a real editing studio. The split is ownership: Sanity is a SaaS content platform; Prelo is a container the client runs on their own domain and bill.
Sanity is the stronger pure content platform — realtime collaboration, GROQ, portable text. Prelo wins the agency handover case: no vendor account for the client, no per-seat bill, one container that holds studio, API and database on their infrastructure.
Sanity’s export is clean NDJSON. Your agent maps document types to a Prelo schema file and replays documents through the content API. Portable text converts to Prelo’s block content.
No — Prelo’s API is REST with typed filters. Less power than GROQ, much less to learn; agents handle it natively.
Generous for solo projects, but client work hits seat and dataset limits — and the bill lands on whoever owns the account: usually you.
More comparisons: Best headless CMS · Prelo vs Strapi
Free and open source. One command, and the client gets a login instead of a Loom.