If you search these forums you will find countless threads on this topic. But AV and even the virri do chnage over time and the best AV [in a persons opinion] will change.
NAV 2004 is an excellent AV [even if i have myself] and you cannot go wrong.
Likewise other AV's are all perfect in there own way.
NO AV is 100% effective but as long as you keep it updated you'll be fine.
I say keep NAV2004.