Difference between Classic and Claim based Authentication in SharePoint 2010

Classic Based Authentication :

•  You cannot configure the Forms based authentication if your web application is using Classic Mode Authentication.You can convert a web application from Classic Mode Authentication to Claims Based Authentication. However, that can only be done using PowerShell commands and its an irreversible process.
•  Classic authentication supports authentication types like Kerberos, NTLM,  anonymous.
•  Classic is more commonly seen in 2007 environments.

Claim Based Authentication:

•  It enables authentication from windows as well as non-windows based systems. This also provides the capability to have multiple authentication in a single URL.
• Claims based authentication uses claims identities against a against a trusted identity provider.
• Claims are the recommended path for new deployments in SharePoint 2010