Avast is far superior to AntiVir,I won't even bring AVG,I have used both AntiVir and AVG extensively before becoming a permanent Avast fan,so have many of my friends and colleagues who after having used various programs,permanently settled for Avast,AntiVir doesn't even come close to the protection module of Avast,no web shield,and only the pro version of AntiVir has mail scanner in it.Another important aspect at least to me is the option of boot time scan which is important for infected system files which can't be cleaned while in Windows session,you have to clean them at boot time,only Avast has this feature of all the three AVs mentioned in this thread,so in the end,balance is heavily tilted toward Avast.