There are other things that you need to take into consideration when choosing an AV, detection is only one element (an important one) you need to look at, Antivir doesn’t offer the same functions as avast now if what is missing is important to your needs, so when choosing you need to also look at features.

Some AVs only support Outlook and Outlook Express in their email protection or don’t offer P2P or web scanning or Instant Messenger cover. There are ways to have one resident AV and another on-demand AV scanner which will bolster overall protection. It used to be possible to have Antivir as an on-demand scanner, but I think that changed with the latest version. BitDefender free is an on-demand option that some use as a backup scanner that or many of the on-line scanners.