Avast was great 10 to 15 years ago. These days it's far too bloated. I ditched Avast back around 2010 and switched to MS Security Essentials.
I'm about to do the same. I've been with Kaspersky for many years, but have heard really great reports about MS Security Essentials. Only thing that has been holding me back with taking the plunge is that it belongs to Microsoft. I'm very much Microsoft averse, it's much too large and we've given it too much power. If I have a choice to support its competition I'll try to do that, although I am guilty of "whoring" from time to time, like changing my home page to Google a few years back. I'm as Google averse as I am Microsoft averse for the same reason.and switched to MS Security Essentials.