Norton or AVG: Which Anti virus is better?

Hi!
I used different kinds of Antivirus in my computer but I am not satisfied. I reinstalled it and now I am looking for the best one. Can you help me to decide which is better between Norton and AVG. For AVG the advantage is that it is free in the internet, free download so I will not be using $$ to have it. Unlike with Norton that I have to buy it in store.
But this is really not that big deal, the important thing is what is the best among these two Antivirus. Which one do you prefer guys?
Thanks
