SEP small business is good - great management console - SEP full is too bloated - but can handle 10K machines at 4 locations around the world with clustered management servers.
microsoft forefront - not bad either.
Mcafee? hellz to the no. the only good thing they had was the security appliance which intel bought lol.
iirc forefront (and its little brother MSE and its even smaller relative microsoft malicious software removal tool) and SEP are highly rated. Enterprise can't afford false positives and need to see the whole picture - location and user aware profiles for local and roaming users (desktop/laptop/thin).
What i'd like to see is a good AV product that can run on the hypervisor beneath the o/s -
Just use Microsoft Security Essentials. Free and pretty lightweight. I've had nothing but good experiences with it across all the computers I've installed and used it on.
Sure that is good but for enterprise use and management, you will need something else.