I use Avast home, never a problem. Haven't used Kaspersky, but here's some pretty good reviews of a few AV's, "k" included (doesn't rate too well in the latest version, NOD32 gets the nod here.)
http://www.scotsnewsletter.com/83.htm
Of the freebies, Avira scores best at AV comparatives (if you put much stock in those...it's a guide), almost as good as the top pay AV's. Except it doesn't have POP3 in the free edition.
The best kind of defense is layered. Nothing wrong with having a few applications from different vendors. SIf one of them gets disabled, you still have some defense. Antispyware is probably as important as AV these days. And a good trojan killer is a must.