Hi,
There is nothing such as a good antivirus or a bad antivirus. It all depends on which one keeps u secure, primarily depending upon ur usage and activities u do on ur pc. I would say that avast is as good as kaspersky or for that matter mcafee is as good as ESET.
In my opinion, the best antivirus would be the one that uses the least resources, does its job and is user friendly.
However, to the question here, weather to go for a free or a paid solution. Well again, it doesnt really matter, if u got free or paid, an av should do its job is that what matters.
So, if i were to make a choice, i would walk with ESET smart security, my reasoning, it is lite on resources, does it job well and is always accurate, a complete solution for ur pc as it comprises of antivurus, antispam, antimalware and a firewall.
I am glad to be using it, no matter even if it is paid, but it keeps me well protected, what matters at the end of the day.