Both are very good but oversized. I run Norton but only because of Some bad experiences with mcafee. They are both VERY difficult to remove. I have spent hours editting the registry to get rid of both of them. It comes down to a personal preference.
I personally don't use an antivirus program at all. In about ten years of regular computer use, I have only gotten a virus once, and I think one of my family members did that. It was the one where it forces your computer to restart randomly (the I LOVE YOU virus, I believe). Maybe I'm lucky, but I also have an understanding of how viruses are propogated, and I know what's safe to do, and what's not. For example, using Windows Update: safe; running an executable file in an e-mail from someone I don't know: unsafe.
I think it just comes down to common sense, and I've never found an antivirus program necessary. I used one a couple times just to see if I had viruses I didn't know about, but nothing. Adware works the same way. Don't run ActiveX content on sites loaded with pop-ups. Don't download cursor or screensaver programs. Always read the fine print when installing a program, especially if it's freeware. Almost all freeware these days comes with built-in adware/spyware. Once again, use your judgement. That's the best tool for preventing viruses, in my opinion.
Of course, I'm not saying don't use an antivirus program. By all means, go for it. Plus, they're a must for any server-type computer as they are most vulnerable to attacks. It just depends on how comfortable you are with not having it.
I say Notrton I used mccaffe and its gets really annoying because i had a little adware on my cpu and everytime it would send me a pop up telling me about it event htough i removed it all and it just gets annoyong especially when ur gamign
PCcillian is top rated, above both of those ad filled large coorperation things you guys call Antivirus. Norton bugs you to death, McAfee does its job halfassed in many cases, sometimes it is ok though. Norton is just annoying.. http://www.trendmicro.com/en/home/us/enterprise.htm