BitDefender Free Antivirus is very buggy, I took it for a test run and was very unimpressed by it. There is a major bug in the scanner which automatically deletes all detected files without any warnings (including false positives). Most other AV's put detected files in their quarantine by default, with BitDefender Free Antivirus there are no options to change its behavior.
I lost several good programs and files which were falsely detected and deleted without any warnings. I contacted support online chat and they didn't offer to help me because I didn't have a paid license. Their support forum is useless.
Other issues include uses more resources then Avast, slows down web browsing, has a lot more false positives compared to Avast and slows down opening Windows Explorer, applications (even media files).
Because it is no secret that Avast Free is much better and gives free users good support in their forums.
Enjoy!!