Don't think that I can tick anything. I tend to research which is the best but in this case was swayed by the fact that I got Kaspersky free with Barclays. Strictly speaking this isn't "free software" and I don't always look for free software. I don't always go with the cheapest offer although this was the case this time. Would have liked a box marked "provided by ISP or online banking".
started off back with first pc in 1995 came with 1 year norton firewall & AV got used to it, after couple of years tried zonealarm not sure if its still around, but crashed my pc causing reformat, did not get on well with AVG just did not like it, Avast was OK but prefered norton as I knew my way round it so well and knew how to sort its faults that came up now then.
now use norton 360 ver3 and well impressed with its speed and performance especially after going through the sluggish days of norton.
always cleaned 100% of the few inections I have had, not sure if the free ones are so good in that field.
I chose Eset many years ago, as it was touted as the best in reviews, tests (eg the Virus Bulletin) and forums. Have stuck with it ever since (and upgraded to the Security Suite from the AV as soon as it was released). I can only say it's always performed flawlessly without any hint of slugging performance. So I've stuck with it. Even the anti-spam works pretty well.
Would I change to a free AV/Firewall - no chance - just look at what they don't cover, or how they affect performance to see why. Small beer, the money to have peace of mind with expensive data.
I do, as a backup, also use two free anti-malware programs, but they only ever find the most innocuous stff.
I have tried several free AV's, Kapersky free trial crashed my machine and only way to get up and running was to uninstall it, Avast was always asking me to use paid for version, only one i would use now is good old AVG FREE, still in my opinion one of the best around.