Ok, I must admit, I think I over-exaggerated on point #3.. The current AntiVir version(w/ the anti-rootkit capability) might have bigger definitions files, but the older versions(AntiVir w/o anti-rootkit) takes up much less space than any other AV freeware. Back then avast was not that popular, and AVG and AntiVir were the only MAJOR competitors in freeware AV. It's no wonder so many patronize AVG and AntiVir.
Anyway, going back to the related issue.. All these points I have stated are just my opinions on how to be the better AV, and we should always look forward to changes. Avast, AVG, and AntiVir all have their own strengths and weaknesses.. but based on editors'/users' reviews and overall experience, AntiVir topples them over.
Avast is still one of the best out there, no doubt about it, but it will never be as good as Kaspersky or NOD32..