I work in I.T. and antivirus software can be a bit of a minefield only because most AV software now does far more than just scan for viruses.
When it comes to choosing AV software, purely from a virus perspective, one of the most important factors in deciding which to use is how often the virus definitions are updated. The virus definitions are how a virus is detected and removed/blocked. New viruses are released every day so the more often the definitions are updated the more protected you are.
In the past it was always the big names like Norton, McAfee etc that had the most up to date definitions. These days everyone is about the same. For business use there is still an advantage for going with a big name but for personal use any delay in updating definitions is usually only a couple of days and often it's the user that is slower at applying the updates than it is the company releasing them.
As I've mentioned, these days most AV software also offers many more security features like Firewalls, E-Mail scanning, phishing protection etc etc. If you aren't very computer savvy then these can be a useful extra but the downside is they can often slow down a system. Norton Internet Security was really bad at this but it's improved since (Personally I'd never install Norton again though).
Ones I've used before and can recommend are:
FSecure - Not used it for a few years but it was very reliable, didn't slow a system down at all and just quietly did what it needed without pestering the end user all the time.
McAfee - Very similar but it would give more false positives than FSecure
Kaspersky - If you can configure it properly it's very robust and quiet but if you don't it can be a bit of a pain. Also at the moment the UK government says it shoudln't be trusted because its Russian. How much of that is backed up by hard evidence and how much of that is just Political huffing and puffing nobody knows.
The thing with all AV software though is that they will detect false positives. A false positive are when it detects things like a file has been changed which it believes to have been caused by a virus but in fact was caused by a legitimate piece of software on your computer or the properties of a file change etc. There's not a huge amount you can do about these things other than altering how and where the AV scans but this can mean making things less secure. Unfortunately most alerts in AV software don't give plain English instructions on what they mean or what the problem is and most people won't know what all the thousands of files are or do on their computer so to a certain extent you have to just rely on the software or know how to safely quarantine files and determine what effect that has had on the rest of your system.
Should you change to a different AV? If you are only worried about the notifications then not really no. You might find that switching to another might mean you don't get those particular notifications but you'll get others.
Is Avast any good? Sure. There are better and personally I'd probably go for a paid version but that would depend on how much I used the PC and what I used it for. If I was downloading lots of things and also programs on a regular basis, I'd buy a better AV program. If I was more just browsing the Internet and E-Mails than I'd probably stick with Avast.
