No, the units are the same. It's the mission that's different. Rather than walking far away from your core, finding resources or other civs, keep them stationed around your cities to "bust the fog" of war. Barbs will not spawn within X tiles of a unit (I forget what X is in Civ IV). By using them as sentries, your workers can build improvements in relative peace."Getting fogbusters out instead of warriors or scouts running around curiously."
By that, you mean builds units more powerful than warriors to be more effective against barbarians when we send them out to places we haven't settled yet?