Share 'The best Anti-Virus Product for Ships ?'

Even though we use VSAT on almost 90% of our ships, Anti-Virus is still a problem when downloading the daily updates. MCafee for example, wants to pull down almost 10Mb daily which doesn't cost us any more but can be pain on a 128Kb link. Does anyone have any good experience of AV products especially those of which download small updates ? Sophos ? AVG ?