avast v6 is the lightest as it can run on some pretty old computer. If you set it correctly, you won't feel a thing. Scan also very fast. MSE scan is slow. Avira got updates problem often. Beside, if you look carefully, avira updates are few days old updates. They never give you today's upddates. Avast updates are fresh.

This post has been edited by Ramjade: May 17 2011, 09:54 PM