I've used several different firewalls in the past 12 years. I believe that ZA works just fine for the "newbie" and the average computer user. Its one that I would recommend for most users to have onboard.
I have also used Comodo's firewall application and as previously indicated, found it to require more configuration input on my part. Not to say that a newbie shouldn't use it, just that you should take the time to get to know the application and how to work with it so as to get the best from the software.
I like both of them, but then I've spent enough time with each to see how either would best suit my needs.
One thing I discovered early on was that the application being replaced needed to be completely removed PRIOR to the installation of the new firewall. Not doing so invited a system crash and re-installation of the system.
I've stayed with ZA.......... for the most part, but upgraded to the Pro version because of the additional features they offer with that package.
Still, for the average user, I think that the 'free' option is mostly adequate. What needs to be addressed, by each individual, is the extent to which YOU are willing to go to for keeping your system free from attack..... and have no doubts about being attacked. It will happen.
Being careful of where you go and what you do is just as important as applying any sort of "safety barriers", such as a firewall.
There are several other "firewalls" around.
Most of which I didn't much care for for various reasons.
Mostly it had to do with trusting them to best protect my computers.
What most users do not understand is that there are NO perfect solutions and thinking that you are "safe" is inviting disaster.
Hope this is of help to you.