Ad-Aware Free uses both Vipre and in-house engines, there are some performance issues with it [which Ad-Aware were reportedly working to fix], not to mention the cloud hanging over the practices of their owners [more in this MT
thread]. Once revered, it has fallen into obscurity, and although they are trying hard to get their mojo back, you have to opt for Ad-Aware Total Security to be able to use an OEM version of G-DATA [contains Avast, BitDefender and Ad-Aware engines].
Outpost also uses Vipre AM engine, I think, which although VB100-certified is adequate and the "weak link" in this suite of contrasting components. The strength of OSS Free is in its firewall and proactive protection - excellent HIPS that comes pretty close to the prowess of Comodo. Nevermind the rhetoric about this being the first fully functional free security suite, the original release suffered from a number of usability issues, and, dare I say it, borderline disrespectful attitude towards the public - initially you could only update your definitions once a day. Luckily, these have been fixed, but AFAIK the Free still trails way behind the current paid edition, which brought considerable performance and functional improvements.
And there it is - CIS Free. Light, tamed and behaving way more restrained than before, lots of features - Defence+, auto sandbox, cloud-based antivirus and behavior analysis, SecureDNS service... The erratic behavior and statements of the CEO are at times cringe worthy, the company has had its own controversies, but actions speak louder than words, and CIS Free is enough to make you forget the latter.
CIS Free for me.
