Antivir has those better features than Avast (for me):
- better Guard scan (when you download files and browse the internet)
- a better and most up to date virus definition files. Avast is known to not update quickly their virus definition with the last virii found.
- non intrusive for me because you never need to restart your PC when installing/updating/removing antivir and also antivir do not refresh your screen every minutes, something avast does all the time
- antivir has a rootkit detection engine (I don't think avast has one)
- avast didn't detect the adober virus I got when I inserted a USB key with it. So it was installed on my PC
🙁 Strangely, avast detected it when I choose the exe in the scan engine => avast has a bad guard scan engine. Avast also didn't detect another virus I got some times ago.
But now, I always use antivir at home + virustotal and another online scanner because using any progs from not 100% sure sources.
NOD32 is also a very good antivirus but not free.
You can check some online AV comparatives like
http://www.av-comparatives.org/ to have an idea.
If you can read french, here are 2 great topics to read:
http://forum.malekal.com/ftopic3528.php
http://forum.malekal.com/ftopic3123.php