My knowledge of the halberd is that they are more or less the swiss army knife version of a polearm. You could use the pointy end to fend off cavalry (charging into a row of pointy spears just doesn't work), or you could use (if you had one) the hook on the opposite side to yank the rider off their horse. Alternatively you can use the axe part of the halberd just to cut through people.

It really just depends on the situation, I assume.