A2: too many false positives, very hard to update.
Edwido does not work well for me, again the false positives, interaction with other programs.
SwatIt I never used :
AntiVir, like you said, does not have any advantages over avast.
NAV: seldom installed properly, never uninstall, processor intensive, unbelivable support.
AVG: not support for free version, only in English, terrible updates. Easy and good with emails. That avast could do better 
System Security Monitor works well to that ones who does not install too many applications for test…
So, we got it! 
I could not say it better 8)