In case you're interested here are some AV reviews:
http://www.av-comparatives.org/seiten/overview.html
The website you recommended mentions that Norton AV (Symantec) is one of the better antiviruses out there. At least according to the little rating system they have going on.
I build and service computers, networks, etc. for several businesses in my city. I used Norton for many years, and many of my customers had it installed on their workstations. (windows based)
And I have to say, based on my actual experience of Norton, it's possibly the worst AV on the market.
It's easily defeated, doesn’t see or cant remove many common trojans, and can hog resources, including cpu time.
AVG Free, on the other hand, just works. And catches anything trying to infect me. Without killing performance.
I wouldn’t place a lot of faith in anything they have to say about comparisons. I think testing and actually using a product are very different things...