[J-WO]

Surely there's a Q.E.D logic in the fact everyone used the phalanx and then gave it up? If both systems were of equal worth they'd be contemporary with each other right up until the fall of Rome. Rome's later enemies would have adopted the Phalanx system as a viable reply, rather than ignore it as the outdated system it so obviously had become in the face of the legion.

1- Throw javelins at phalanx and weaken it.
2-Use big shields to soak up Phalanx's attack.
3-Use short swords to cut down spear heads.
4-Get in close and stab a bunch of guys now holding long sticks.

With a few exceptions, this seems to be what happened. War evolved.