i have used both and barracuda in my time, i prefer SMG.
The Forrester Wave™: Email Content
Security, Q4 2012 Nov 15 2012
http://www.computerlinks.de/FMS/22423.the_forrester_wave_email_content_security.pdf
supports great integration with DLP
it lookedd at all of these Barracuda Networks, Cisco,
McAfee, Proofpoint, Sophos, Symantec, Trend Micro, Trustwave, and Websense.