Dark Lord of Tech :
Avast FREE has been a good proven winner over the years.
I wouldn't say it is a winner, especially when you look at AV-Comparatives's reports. Avast definitely has some issues in areas that just aren't present in other free wares, even in ones with lesser protection. Avast, as of the last AVC reports I saw (published early/mid this year), did not make me feel comfortable. High numbers of false alarms, and a decent amount of resource consumption, take it down quite a few notches in my book.
I've not seen too many serious security professionals highly recommend Avast, so I would be reluctant to call it anything close to a "winner." If anyone wants me to scrounge up the old post that I made, comparing Avast to a couple other security wares, then I will; it shows exactly why i wouldn't recommend it, based on publicly published reports.