I use AVG antivirus free version, It's best and the main thing about it is it's free. so i prefer AVG free version.
My PC was very badly infected with virus when I installed Quickheal hearing its name. Quickheal is not a standard anti virus software. It is very difficult to relay on it.
Avg is decent for free. If your looking for the best of best that would be node32. There is nothing better currently available to the public. This isn't based on opinion, it is fact!