Lusotann, bravery is good, relatively numerous and easy to get, their formations maybe isn't as tight, but they got really disciplined army that could overmatch their Romaioi and Kardechoi counterparts. Their weakness is complete lack of scary units...
(I Vote Lusotann)

But the most effective is Sweboz of course... especially when see their (the Luso's) sky-high upkeep that could feed more pantodapoi phalangitai....