They all d the same job and are as good as each other. I don't use a firewall but many of my friends use Agnitum. It works quietly in the background and uses a minimal amount of resources. however I would just choose anyone, there is litle point in worrying about it. G
Agnitums Outpost works well for me. I first used Zone Alarm and upgraded to Zone Alarm Pro which prevented me from accessing any of my emails. I emailed zone labs for help several times without success.
I could get my emails if I unistalled Zone Alarm Pro. I posted this problem on this site and eventually opted for Agnitums Outpost which has worked well ever since.