Everyone responding is going to have a different opinion because AV programs are a personal choice thing. All I can do is report my experience(s) with different programs and which one(s) I prefer and use.
I have purchased ESET NOD32, Norton, Kaspersky, Bitfinder and McAphee. I've probably tried every freeware program out there. At the end of the day I have settled on using AVG Free for anit-virus protection AND Malwarebytes (free) for malware protection. In the 4+ years of using this combination I have never been infected by a virus, worm, trojan, etc. If you are bound and determined to purchase your AV program, I would probably settle with Bitfinder Plus (although it does have a free version and the #2 on my AV list).
The only AV program that I would stay from is Kaspersky. I know some people give this the highest rating and that's great. After downloading the installer link It proceeded to install a 256MB program onto my laptop. Windows ceased to function after installation (explorer.exe became corrupted). But that was just my experience.
So at the end of the day it's AVG Free + Malwarebyes for me. Good luck with your decision.