Hmmm AVG is free and very competent! Avast is free and cannot comment on it but haven't heard anything bad about it. Norton Internet security.... Heard tons bad about it. For one thing updates for Norton antivirus is every Wednesday.... as opposed to AVG which is every single day and that means your probably more up to date using AVG.

Here is a link to ratings of Norton Internet Security Cnet's Review!

Norton Internet Security 2005 (NIS 2005) is a suite of four utilities designed to keep your PC safe from criminal hackers. While components Norton AntiVirus 2005 and Norton Personal Firewall 2005 both lived up to our expectations, we found Norton AntiSpam 2005 to be sluggish, and we're particularly disappointed with Norton Parental Control because of its reactive rather than proactive behavior. This suite of tools also dramatically slowed our test system. If you're going to pay $70 for a security suite, all the components of the suite should work smoothly, get the job done, and work together. In our opinion, the new tools are not compelling enough for existing users to upgrade. If you're new to Internet security suites, in our opinion, nothing beats ZoneAlarm Internet Security for comprehensive PC security--not even Norton.
This is just my humble opinion.... I run components/software from different manufacturers as I have found no company does everything the best! But to really find out about software your considering... Type in something in google like "Firewall ratings" and "Antivirus ratings". You can also search for "Parental Controls" if need be. Trust sites like Ziff Davis and CNet as they are Huge Top Companies but may not be as thorough as smaller tech companies on their reviews. But they won't lie or decieve you which is why I like them as a preliminary guidline before using other reviews! Lastly I listen too/read individual reviews. Many people who post those are not even sure how to test something. If it works and does the basics they will give it a high review. If they are not even competent enough to read the user guide/help files and cannot get it working, then they may give it terrible reviews! Many times 10,000 individuals using a piece of software will post alot of short commings in the software some tech reviewers and large Company reviewers may miss.

Be aware some of my favorite software I use is free! Free is great! Check them out first always!