I use both McAfee ver 7 and Norton on XP machines and they are about as good as each other. The auto-updates work fine on both if you use care in setting them up. They are completely transparent if that's what you want or they will ask politely if they may go on line to do the business.
Manual and Auto updates with McAfee seem to be free for life but the Norton updates cease if you don't pay more beer tokens. Both will tell you that they can't guarantee successful co-existence with ZoneAlarm but if you ignore the warning they seem to get along quite happily. Understandably both McAfee and Symantec want you to use their own Firewalls
The is a problem with McAfee on the XP Pro machine on which I'm running a trial with the Beta version of XP Service Pack 2.
The "Console" won't start. All this means is that the "Scheduler" won't start and therefore there wouldn't be any scheduled auto scans if I wanted them. As I don't want any, it doesn't matter. .
So, for the moment, until that little bug is sorted, and if you can go with the paid-for updates, I'd have to say Norton is the better.