There must oppose Qihoo has full virtualization (full sandbox) .Correct me if I'm wrong friends.Best "free" security suite (with both full virtualization and firewall) is Comodo.
Best "free" security security suite (without full virtualization and firewall) is Qihoo.
Best "free" anti-virus is Avira - or - Bitdefender Free - if it works without too many problems.
Comodo is best opoɯoƆ...
Other than that, there isn't much to debate regarding "free" anti-virus.