Telnet access allows clients to take advantage of easy maintenance of their sites in a UNIX shell. Clients are able to roam through their sites, change permissions, move files, delete files, and debug scripts. Compiling programs is also possible. Shell access also allows for manipulation of mySQL databases. Since you are working directly on the server, any changes you make to any of your files are done right away, and therefore update content on your website usually quicker than through FTP.
SSH add security by encrypting terminal connections and secure file transfers decreasing the risk of others finding your password. Note : On Monster and Ultimate Unix accounts you can access the shell via Telnet or via SSH2. However, we strongly recommend that clients utilize SSH for shell access.