I'm talking from NOT AN AVAST! USER OPINION NEITHER AVIRA...
But I'm saying this...
Avira was great back when version 9,8 and so on... but their new version, tested it, it could not block any zero-day/hour threat.
Avast! blocked something like 6/10 with free antivirus, I would go with Avast! cause Avast! has improved alot by version 4.8
I think Avira this way:
Older version that are free, but better than payed, their next version shall fail.
Regards,
Armin.