Which antivirus software you use is going to be subjective in my humble opinion.
I have been working in IT for about 17 years now and been building/managing my own computers for 25. That said, nobody knows everything about viruses and malware, there are plenty of zero-day exploits. Each antivirus may catch or identify some things that others don't. I put whatever is currently easiest/best for me or DW. I used to run AVG - it was decent for many years. Now I run Avast with Malwarebytes scanning occasionally. My Windows XP/Ubuntu dual-boot machine has not had a virus in 5 years.
Microsoft Security Essentials is the "low" end, you get what you pay for. In some cases that's all you need. I've never used Kaspersky but some of my tech friends like it. Mcafee isn't my favorite, we had many issues with it when I worked for a contractor at a small business. I used F-prot (F-Secure) a long time ago and it seemed to work fine. Eset NOD32 antivirus is no longer free to use for the year (like AVG and Avast, etc)
The thing people forget about is your surfing habits and your browser. IE 10 has definitely improved but I've stuck with Firefox and sometimes Chrome because they don't have the same security vulnerabilities; you can also put in some addins like Adblock. Obviously if you go to sites that are questionable or that purport to offer "free" software that you'd typically pay for, you're increasing the risk.
I also occasionally scan for rootkits but I haven't found any. I used Rootkit Revealer and Rootkit Remover for that.
I've also used online scanners like TrendMicro and VirusTotal occasionally but mainly to compare specific files to files others have reported. There are sites out there that "measure" other sites' safety and reputation, like Webutation, Trendnet and Mcafee (Trustedsource.org). If there's ever a question about a site, just don't click! :)
There's much more to computer security and I am now rambling :)