We are moving toward Microsoft Security Essentials as our recommended antivirus package. It is free and has a low foot print. Also it never pesters you to upgrade for money. Lastly it is backed by Microsoft which is means at the very least it will install and play nicely with their operating systems.
In general antivirus applications that have Internet Security built into it, we try to avoid. We find that these personal software firewalls can cause more trouble then they are worth. First of all we are not sure exactly what they are protecting from when most Internet usage is already behind a secure firewall appliance and it is seldom if ever when you are actually placing your computer on the public Internet. Please read this following article on natural firewalls.
The negative side to Internet Security is it might prevent you from accessing something you do need, such as installation of a piece of software or allowing remote access to that computer. Overall Internet Security may be useful and may protect you in certain situations, but on balance we find it to be too resource intensive and an element of confusion.
Often bloated antivirus applications can sometimes be the leading cause of your computers general slowness. When the security application is given the ability to fully scan and control every aspect of your computer, such as SPAM prevention, Internet port blocking, etc, the act of protection can have a reverse unwanted effect. This is to bog down your machine.
On top of all this malicious applications that get on your machines called spyware or malware bypass your antivirus easily, so it is not surprising that the topic of antivirus protection because a bit confusing to the average user.
Overall we do recommend a low footprint antivirus application that does do regular updates and provide real time protection. We try to avoid Internet security & SPAM blocking application and try to have the network or email provider give those types of protection. Lastly we highly recommend users still be prudent in the what they click on via the Internet, because malware is prevalent and can bypass your current antivirus protection.