Tor: Are onion sites safer than ordinary websites?

Short answer

An onion service hides the server's network location and encrypts the Tor-to-service connection without an exit relay. That does not make the site's content honest, its software secure, or its operator trustworthy. Use the same caution you would on any website: verify the address, avoid unexpected downloads, and do not disclose sensitive information merely because a page ends in .onion.

Sources

Tor Project: Onion services, Tor Project: Tor Browser best practices.