The key difference
Overskill focuses on getting a working app workflow together from a description. Replit provides a broader development workspace where the user takes more responsibility for the development environment and production setup.
Who each suits
Overskill is worth testing for operators and founders who want a more guided path to a working application. Replit can suit developers who want a familiar coding workspace with AI assistance.
Test before deciding
Build the same small app in both, then compare authentication, data persistence, integrations, deployment, debugging, cost and export.