[Bioclusters] About RSH/SSH in Cluster

[Yun He]

Many applications in cluster need password-free environment, such as OpenPBS 
or Torque, usually, there are two ways to let us login into different nodes 
of cluster without giving a password, one is to use rsh with .rhost file in 
each home directory, another is to use ssh with RSA key authorization.
Which is better? Which is more efficient ? 
If I use ssh with key authorization,  could I need to use an empty-password 
private key ?

Thanks

                  Jarod