My advice to anyone who wants to listen is to go to reputable rating site and see how well the AV program they are looking at is rated. I have used this one for years and it always be spot on with its ratings. There are other sites out there who do the same thing and you can search them out and read them to. The biggest thing I have found is that most free AV programs do not have their programs tested.
The best thing about this site, that I have found, is that if a AV company request that before being tested that settings be changed from to default to higher sensitivity they point that out. While a AV company might test high they will not perform as well if you just run in its default setting.
While I do "dis-infect" some PC's now and then a common reply is I use this or that A/V protection. While often it maybe free or common commercial pgms. they did get through. I offer this link as some proof that free A/V may not cut it. End users get upset because they think they're protected but got into trouble. It still depends on where you surf also.