NOD32 is without doubt the best AV available. I have used it and comment through experience comparing it to Norton

(NEVER) AVG and Avast.
NOD32 should be called NOD 0.0000000000001
Very light very quick and very secure.
Personally having 2 gig resources are not an issue and at the time of a new HD instal i chose to go Totally free.
I use Avast whcih i just like the feel of. I have switched of all the auto BS so resource usage is pretty light. I am a habitual updater so no stress.
Avast updates well frequent and does a good job for me and i also use Ad aware and spybot very regularly. Twice a week to be honest.
Av's are a personal thing and you have to feel secure as well as be secure. Here a horror story and you crap yourself and switch

After acting that way for years i am happy to settle with the one i like which is Avast.
So if you have to pay to feel secure about your AV or you are a resource junky or genuinely short of resources then go with NOD32. Otherwise Avast will do the job for Nowt.
Edit.
I also use Ewido a new addition to my anti V arsenal.Great prog.