Barbarian factions certainly get nice armies, with the noble/hero/elites being really awesome. Especially if you compare the possibilities of RTW barbarians with EB, the team has done a splendid job.

The only barbarians I have really played are the Arverni, which I really liked at first, uniting Gaul. Then I established a sturdy border at the Elbe and the Ebro and destroyed the Romani. Although I could invade Britain and expand in the Mediterrean I don't really get the imperial feel from midgame I get with the Romani, Hellenic and Eastern factions. It's easier to roleplay huge empires with those in my opinion.

Happy campaigning!

~Fluvius