The Hunt for the Ultimate Free Antivirus Software

I spent some time researching top-rated, but free antivirus security software for both Mac and Windows.  There are far more free antivirus software solutions out there than listed here--I focused solely on those receiving positive reviews from respectable sites and/or testing labs.  I also tried to limit the search to those offering both Mac and Windows versions.

This hunt was sparked by a personal incident where malware slipped past my AV software defenses.  For obvious reasons that software did NOT make the cut.  I needed to find something better, so the hunt began.  Here's the list I compiled along with my snap impressions.

Avast
Good
* web reputation score (browser plugins)
* blocks malicious URLs
* remote assistance feature

Bad
* It installs Google Chrome and sets it as your default browser.  Ugggg...I recall this being easier to avoid on Mac.  I don't remember it even asking me on Windows.
* not so good at blocking phishing URLs

AVG
Good
* runs well on my Windows virtual machine
* slick, easy-to-use interface

Bad
* a few more up-selling attempts, banners, ads, etc. than others

Avira
Good
* high ratings from the testing labs
* runs well on my Windows virtual machine

Bad
* not as feature-rich as other free offerings

Bitdefender
Good
* high ratings from the testing labs
* remote assistance feature
* incredibly minimalist interface may be for you

Bad
* free Mac version is on-demand only (no on-access scan)
* incredibly minimalist interface may not be for you

Forticlient
Good
* The business-like interface may be for you
* The malicious link blocker / parental control is awesome
* VPN client

Bad
* The business-like interface may not be for you.  Non-power users may find it unintuitive.
* The link blocker / parental control may slow down your web surfing experience.

Malwarebytes
Good
* finds things other scanners miss
* showered with awards and accolades
* can clean up PCs riddled with viruses--even an undead apocalypse zombie's PC

Bad
* free version does on-demand scans only

Trusteer Rapport - HONORABLE MENTION
A heartfelt honorable mention goes to IBM's free Trusteer Rapport software.  While it isn't full-blown antivirus software, it takes a unique but valuable approach to online security by validating URLs and blocking malicious ones.  It's essentially a trust-building mechanism--making sure that the bank website you're visiting really is the bank website you think it is.  I've encountered no issues with installing it alongside AV software.

NOTES
* Avast & Forticlient crashed my Windows virtual machine when doing a scan, so I didn't have much luck with running these in a VM environment.
* Turn off Mac's time machine feature and dismount network volumes before running a full scan.  Some scanners will try to scan all the backups and network volumes, likely choking and freezing in the process.

CONCLUSIONS
* My overall personal favorites are Avast and Forticlient, as they seem to offer the most bang for the (zero) buck.  I recommend installing one of those, along with Trusteer Rapport.
* My personal favorite for my Windows virtual machine is AVG, coupled with occasional Malwarebytes on-demand scans.