McAffee sux. Norton sux. They both use about twice the resources of NOD32, Avast and AVG. They suck. Symantec is alright but that still uses just a hair more than NOD32 and Avast. Kaspersky, well that is know to break down on Vista.
This is all personal preference. We can argue over this all day.
Norton AntiVirus 2008 - Efficiency test - Neowin Forums
AntiVirus Comparison - Google Search
TEST: Norton Antivirus - Beta-Place
There the first one and last one are actual comparisons done by people. The last one is done in VMWare with the same setup. Each shows how much resources a system uses with each applicaiton installed.
But again it is personal preference. I used Norton and swore by it for so many years. Till i tried Avast. Then it found over 50 viruses and malware on my PC that norton said was clean. Since then i have not looked back.