It is much more configurable and if you are into other modules other than a firewall it has those too, me personally I want my firewall to be just that a good firewall.
I bought the Outpost Pro version many years ago on a great lifetime license offer for the same as a 1 year license, couldn't resist. At that time I was using the outpost free firewall, that however was version 1.0 and it lagged well behind with little development. More of a hook to have you consider the paid version. It is only recently that the 6.x free version was released and it is a fine firewall.