Windows 7: AntiVirus, or no AntiVirus?

My NIS 2012 is going to expire on the 31st, and I've not been planning to install a new AntiVirus, as I feel I'm under control and that all I'll require is the Norton toolbar which has recently been made available to download. If not, I'll be trying BitDefender, as I've heard it has the best detection and lowest false positive ratio, along with even lower resource usage than Norton.
What do you think I should do?

I use MSE and Windows firewall have never had any problems so far any how .

ditch it all and use Microsoft Security Essentials - Microsoft Windows and Malwarebytes : Malwarebytes Anti-Malware removes malware including viruses, spyware, worms and trojans, plus it protects your computer for on demand scanner

There's a listing of AV's here & you can weigh the pros/cons of each.

What's the Best Anti-virus?

Many people in this forum use MSE combined with an on-demand scanner, such as Malwarebytes.

I've thought about the same, I'm just not keen on any performance drops due to Anti-Virus.

MSE is very light on system resource usage and is very unintrusive in general, the only time MSE ever bothers you is if it possibly found a virus or some other kind of malware. MSE also probably gets along well with Windows the most out of all AV software, owing to the fact MSE is being maintained by Microsoft themselves.

What kind of performance drops are you anticipating? Personally, I'd rather give up a couple hundred megabytes of RAM (out of the 8GB on my machine), or 10% of my CPU for real-time monitoring, than to go through the hassle of getting infected, using a previous system image, updating things, etc.

The good thing about AVs today is many of the recommended products like MSE, Avast, Avira, Comodo, etc are totally free. You could always try one for a week or two, see how it actually performs on your machine, and then decide if you want an AV or not. Just remember to use an official product uninstaller to remove all traces of the AV product before installing another one.

Security Software | SingularLabs

I have been using Bitdefender , In my opinion all antivirus softwares have one or another drawback/problems , some may be using heavy system resources, while another may be poor in security. Bitdefender is known to be one of the best in detection rate and is light on resources and also being rated highly by the reviewers.No antivirus is 100% perfect and getting above 90% in a review is itself very good.

I never noticed any performance drops from NIS or MSE. I use both (on different systems of course) and I prefer NIS. But I would not recommend to work without an AV program. That would be a certain path to trouble.

Personally I wouldn't run without an anti-virus or Internet protection and almost any of the top makes I would probably be happy with. It just so happens that I have been using NIS for many years and it has kept any malware off my system. I should be more worried than most since I do run as admin - yes, not recommended!

Free anti-virus is fine if it indeed does the job but if you can afford a computer ....