I have tried both McAfee and Norton and settled for Norton. McAfee missed quite a few virus which Norton picked up, Norton has, for a long time, had an on-line weekly update, I think McAfee may do this now.
A word of caution though, I find Norton Anti-Virus 2000, (v.6) does an excellent job, but DON'T go for the Norton Utilities package, this is like pouring glue into your computer.
The second version of WIN95 and both versions of WIN98 carry a lot of their own 'housekeeping' utilities anyway which makes 'Cleansweep', 'First-Aid' and Norton Utilities superfluouse, in my honest opinion!
For every Norton 'lover' you will find a McAfee 'lover'who will disagree with me.