At present (judging by the 1.3beta) Compass does not provide the same set of SSL-related options as mongo shell. For instance:

• There is no way to specify CRL ("--sslCRLFile" in shell)
• There is no way to disable hostname validation ("--sslAllowInvalidHostnames")
• No analogue of "--sslAllowInvalidCertificates" - note it's not the same as "Unvalidated" SSL connection. That option (in combination with others) allows the client (e.g. shell) to present it's own certificate to the server, even if we accept that validation of the server's certificate can fail. The "Unvalidated" option does not allow client to present its certificate.

Essentially, without these options the amount of SSL-related use cases supported by Compass is less than the amount of use cases supported by the shell.

FWIW Even Robomongo does more than Compass: http://blog.robomongo.org/robomongo-rc10/