The cleanest way to compare Mocha and Same.new is on one concrete job: building a small business web app with secure logins, forms, and per-user records. That job forces a real split between them. Same.new is strongest when the work is mostly visual imitation and frontend scaffolding, while Mocha at least attempts the full-stack problem with generated backend routes, auth, hosting, and a built-in database.
That job also exposes the failure modes that actually matter. A pretty dashboard mock can survive messy generated code for a while; a client portal or internal tool cannot. Once the app holds customer data, the question stops being how fast it looks finished and becomes whether auth, permissions, and data isolation were implemented correctly enough to trust.