sykozis :
Sounds like you get all of your information from PCMag....who appears to get paid for their antivirus reviews. Recently (Dec 2013) I used Kaspersky to scan a harddrive. After nearly 3 hours of scanning, Kaspersky reported the harddrive as being clean. Approximately 30minutes later, my desktop was trashed by viruses that Kaspersky missed. I plugged that same harddrive into a laptop running Avast Internet Security 2014, which immediately started popping up warnings about infections. In total, that harddrive contained over 1000 different viruses that Kaspersky (one of the top rated Antivirus solutions on the market) completely missed.
I've not looked in PCMag or their site in years...
I'm also referring to what I've seen by the companies actions and how their product works. Mcafee spams, it seems to be "accidentally" installed on my of my clients computers when they upgrade something else... etc. I wasn't giving any credit to Norton, which I have not used in almost 10 years.
Not all AV programs will catch everything. If there is a time between an upgrade patch and the virus comes into your computer - then anything can happen. You got 1000 viruses? I doubt that... you may have had lots of infected files, but doesn't mean they are actually running. If 1000 were in operation, your system would be non-functional. Anyway here is what happened and what you should have tried out.
Once you got infected by a particular virus, it compromised your AV software.. making it ineffective. Then other viruses got installed on your system. Since your AV software is a walking dead program - you didn't notice. But as you said, you plugged the HD into another computer to run a different AV program. I bet if you ran Kaspersky from the other computer, it would have found the viruses.
When I tests other people's drives for virus, I pull the drive and use another CLEAN computer to do the scanning.
Personally, I use AVAST too. I'm fine with AVG.