I'm no expert, but....
I worked for one. Avast Home Edition is free and it can be just 'okay' as downloaded and installed. It can be great if you know who to tweak the settings. I have used Avast the last 10 years. It only ever had one glitch and it was fixed in less than 24 hours.
The only paid for version we ever would suggest is NOD32. All of the other brands, again, if you know how to tweak the settings you can improve things.
I run Avast with Spybot (the older version and tweaked) set up to auto scan while I sleep.