I have been involved with AV for nearly a decade now and have researched all of the "prolific" vendors.
In all fairness, they all have something within their product that is unique, whether it is as simple as price the management consol, bandwidth utilization or policy.

Personally I found McAfee to offer the best solution based on minimal bandwidth, coverage, policy enforcement, management and policy lockdown. McAfee ePO server is very unique and it allows other useful McAfee Security applications to be managed from the same consol.

Whilst the McAfee suite (AVD) ?Active Virus Defense? is not the cheapest, we are talking about a security product that is pretty much an end-to-end solution.
A major point that needs to be highlighted about this product is that it is not for the average administrator to integrate, as the best results will only come from having a McAfee Certified Engineer complete the installation across your LAN/WAN.

McAfee also offers a range of on-site and off-site certified training courses to allow your own staff that level of competency with their products. Be aware that these courses are a percentage pass course, so there is no ?guarantee? that you will pass the first time round.