Like you, I haven't used the Agnitum Outpost but that's because I haven't needed to. Others such as ZoneAlarm work fine for me. Rule-based systems allow you to configure trusted ports where you will allow traffic for specific programs. In most cases, they set up "rules" before using the system. Program/permission based systems allow you to configure access for trusted programs through the firewall. In essence, they're doing similar tasks, but in a slightly diffferent graphic user interface.

Read the reviews. Although not bad, Outpost is not always one of the favorites.:

PC Personal Firewalls 2004,

Personal Firewall Reviews

Outpost Firewall Pro ... Version: 2.1

Hope this helps.