Chosen axemen are the best infantry unit in the game. I believe they beat every unit in the game head to head (including bodyguard cav units, catas, etc), and they only cost 450 (with a ridiculously low 100 or so upkeep).

BI is still cav dominated, however. So imo all infantry units are a waste (you only need 1 unit to use a ladder and open up the gates for city assaults).