I am currently trying to find that out but, as of yet, my discussion that includes that very topic hasn't been responded to.
I CAN say that, from looking at other topics of the same nature, and having asked Grinler, Kaspersky and ESET NOD32 are both highly recommended by the BC Team. I also know that Emsisoft Antimalware (which is not a secondary program like MBAM but a main AV) is often recommended here.
As a caveat: BC is an affiliate partner of Malwarebytes, SuperAntiSpyware and Emsisoft.
Further, many articles here recommend Avira, Avast! and AVG, but I don't see many of the experts here recommending them in discussions in the forums (but maybe I need to look harder).
According to Quietman, AVG partnered with Limewire, a point-to-point (PTP) music-sharing program, and there is thus concern as to AVG's quality and standards since PTP is a common infection vector. I used to use AVG but it was eventually defeated by malware. This was back around 2008.
I then went to Avira Free, and it was even more easily defeated.
I then BOUGHT Bitdefender and was relatively pleased, but it was not perfectly able to keep my system clean and eventually I was out of cash so I went to Avast!.
I tried out Emsisoft's Antimalware (EAM) as well as Emsisoft's Online Armor (EOA) a year or so ago on a one-year license and, while I thought it did a really good job, it destabilized my system (which may be because it has a dual engine and because my system had problems and not enough RAM). If I had a better system and money, I'd certainly consider EAM.
I have since used Avast! and it hasn't kept everything out of my system until now. I combine it with Spybot 2, which has some active features for free users that MBAM and SAS don't give for free.
The truth is, if you want something free, you're in the same boat as me - you're unlikely to find something that is really going to keep all the bad software out - even if you're careful. There's just too much malware, too many hackers and phreakers, and too many people willing to turn to cybercrime for money. Even buying a program doesn't guarantee you 100% protection. As Quietman is quick to point out - the weakest point in a good system is always the user. Well, he doesn't say it that way, but that's the gist of it.
If Grinler, Quietman and other BC experts are saying go with ESET NOD32 or Kaspersky, I'd say give them a good looking over. If you want to buy MBAM, SAS or EAM, support BC by buying through their affiliate links. (shameless plug for the people who help us all!).
I really wish I could give you better advice. If I do get more info, I'll try to let you know. Best of luck!