"As good as any other"
Hmm - well I think that's obviously not true - any mre than saying a Ford is as good as any other - but it may be good enough.
Remember there is moe than one way to measure "Good"
Is it detection rates that is most important, or how fast it runs or how quickly new threats are covered or how easy it is to use or how good it is at removing infections from a machine that's already got something on it?
Once I would have said that a key consideration is how risky your usage patter is - whether you download programs or visit adult sites but malware authors seem to have become pretty good at exploiting vulnerabilities to the point that something like 6% of home PCs are infected.
In terms of raw infection sites like av comparitives tell you how good some of the software is
http://www.av-compara...et/avc_od_aug2011.pdf
Avast and AVG are middle of the pack - Microsoft further down
If you're paying for one you want to make sure you're getting support - the ability to ring someone up and say "Help!!!"