I cannot see Avast Pro being the best paid AV due to the fact that there is only small features changed or added into the PRO version of Avast when comparing to the free version , I might be wrong...I think people are better off on the free version... I also think there are better paid AVs than avira pro...
Paid antivirus is always best as it contain latest virus definition.
I am using Venkasure Total Internet Security+ ,which is best antivirus i have using and it's cost is also reasonable with great scanning speed and never slows down the speed of computer.
Even the best paid ones out there can't protect against all viruses...Paid ones are not that worth since not all AV can capture all of the viruses malware etc....Better off just getting a reliable free AV IMO to save money