I used to admin a fleet which had the previous version, VirusScan Enterprise 8.0i. It was quite "heavy" when fully armed. I think it's safe to say it was much harder on the system than the consumer version at the time.
One of the features I did like was the ability to create arbitrary behavior-blocking rules. For example, I could create a rule forbidding any .EXE file from being executed from the user's profile, no questions asked, and not only would it block the user's attempts to run napster_setup.exe, but it would be reported to me via the ePolicy Orchestrator Agent. I had upwards of 60 custom behavior-blocking rules designed to safeguard the systems from the users and from worms/exploits, and to report any attacks to me.
From what I've heard, the enterprise versions of Symantec/Norton products were known for being lower in resource usage than the consumer versions, but it's also known that the consumer versions have been getting an overhaul to address that area, so you may want to try a trial version and decide for yourself.