The main difference is that DLO backs up user workstation file data to a shared folder. DLO cannot backup to tape or to removable drives. DLO offers a backup option to manage multiple user's offline and online files seemlessly and a work environment in which DLO will synchronize the transfer of files to the shared folder automatically.
refer: http://www.symantec.com/desktop-laptop-option and http://www.symantec.com/backup-exec?fid=backup-exec
DLO agents are for workstations and Backup Exec agents are for servers. The cost per workstation vs per server is priced accordingly (per worksation agents are less than agent per server).