I have spent so many years using a cumbersome, resource hogging AV, that I eventually got so fed up with it and changed to Avast. The difference is unbelievable.
I have now had Avast for only 3 weeks, but it has performed magnificently without my knowing it is there. Automatic updating with my previous AV, took 6-7 minutes and absorbed all my resources such that I had to stop work until it was finished and this frequently happened when I first logged on. Avast updates completely anonymously with no such problems.
So I must sincerely thank Avast for being such a fine, user-friendly and efficient program which operates without any disruptions whatsoever.
Avast also provides an excellent Email protection.