I don't use free antivirus program because I distrust them. How can free be better than Symantec (beside it being free of course), which I'm currently using. How can free antivirus or rather how can company that offer free antivirus makes money in order to have resources to make their antivirus program better? If it is advertisement, then you will have to let spyware into your system. If it is donation, then maybe it not so free and the program may not be updated if there not enough funding. Also is free antivirus being updated as quickly as the not so free antivirus program?
Symantec is also being use by my company. If company trust, Symantec, then it is good enough for me. The company I'm current with have more than 1,000 employee, and each has a computer. I also have BitDefender Professional antivirus program and I have not try their product yet, but it got to be better than the free antivirus.