These forums are full of people who have jumped ship from the likes of Norton (harder to get rid of [uninstall] than some viruses), and AVG, not even close to avast.

When I uninstalled AVG and installed avast, my first scan found two viruses that had been happily living under AVG.

Just do a search on these forums for Norton and AVG and you will get some idea of what I mean.

HTH David