You see BCB ?
One person had ZoneAlarm installed until it started to give him all kind of problems, then he switched to Sygate or Outpost, doesn't really matter in this case...
Another person had Sygate installed, and when it started to give him some troubles, he migrated to ZoneAlarm...
I know at least 10 people from these forums who abandoned ZoneAlarm because of all kind of problems they experienced on their systems using ZA. I personally never had any problems with ZoneAlarm in my whole life, I was just curious and I switched to Outpost. Outpost is wonderful firewall, uses much less system resources than ZA, but I found some issues, and I decided to go with another one... now I'm using Sygate and after version 5.6, I'm very very happy Sygate user.
As you can see, there are no rules... best one for you is the one that you try, you see you like it better than other Firewalls, and then decide to go with it...
Merry Christmas everyone !