Pontos for me, because of the wide variety on the unit roster next to the phalanx units. (Galatian naked dudes and scythed chariots do nice insta routs together.)

But if I have to stick at a hardcore phalanx based faction, then it's Makedonia. Hysteroi Pezhetairoi (sp?) is just the best phalanx unit in the game, since they are much cheaper than the elites, yet they have almost the same stats. Also their high end units belong to the bests of the game.