Ok exceedingly biased reply… Avast does not come bundled with a tool bar or tweaking programme. It has an exceptionally good webshield to block you from inadvertantly going to an infected website, it has boot scan function for the more resilient malware
The forum here is very good for resolving any problems associated with either the AV or any infection you may get
The system resource usage is very light and does not impinge on system speed
Avast aims to stop malware getting on your computer in the first place hence the various shields
Scan speed for a full system scan on Avast is about half of the comparative AVG scan
Avast auto updates every few hours with no user interaction required
So the main question is what do you require from the AV, knowing that may help us to help you