Avast was the first antivirus I've used since it was version 3. Years later, we got this Windows 7 PC and also my Windows 7 netbook. I heard of Microsoft Security Essentials and decided to try it if it was any better than avast.
The installation was quick and the application is small. The interface was also simple but does not offer much control or any more levels of protection avast has. It also responds slowly on threats. But its unintrusive nature compared to avast made me want to keep it. I'm tired of avast's annoying autosandbox.
A month later, I discovered that my USB got infected by a worm. It came from the PC protected by MSE. Somehow, the worm bypassed the MSE protection and managed to get in the system. I ran a full scan on this PC and MSE detected one worm and a backdoor and promptly removed them. But damn, MSE must be a piece of crap not to detect malware before it reached my system.
Needless to say, I reinstalled avast and uninstalled MSE. At least, I can make avast quiet and disable the autosandbox by changing some settings.