Well, in terms of pure damage, the halberd is about 50% better (I'm guessing the second one is supposed to be warhammer is with title?). If you've got a good shield (big crystal shield, eternium), it might be worth sticking with the hammer anyway--the big shield could be worth 25+ DV and a couple points PV. Depends how good your shield is, I guess.
If you wanted to follow the advice of your sig, stick with the shield.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.