Norton has the tendancy to surpass many types of viruses that are hard to detect. Avg isn't perfect, but it is seemingly much more efficient at detecting problems on a computer. It has to be updated frequently, but that just shows you that the designers allowed for constant improvement and protection for your computer. In the past, norton has also been known to cause problems on computers because it has glitches in the firewall, which, consiquently, is not convenient to turn off as it disables most of your protection. Avg does not require a firewall, is free, and has far fewer bugs and defects.