Spears are great if the target has organs. Spears pierce organs very well, disabling and quickly killing most foes. Against things like solid material FBs, their success varies. Spears are also a tad overpowered now, especially with how often they pierce the brain, which is almost an insta-kill.
Swords and Axes are good for lopping off stuff, particularly limbs. Missing limbs are a huge handicap, and often lead to a quick death. Slashes and other large wounds come from swords and axes as well. This can cause a lot of blood loss.
Hammers and Maces deal crushing damage. They're great for disabling enemies, whether from a broken arm or bash to the upper body. They generally aren't great with killing blows (you can keep bludgeoning an enemy into the ground until their limbs are a paste, and then they might die) but blunt weapons are good for support attacks.
Generally, it's best to keep a well-rounded military. Sword- and Axedwarves are good at delivering killing blows, but may not kill the enemy fast enough because they're still too strong to be hit effectively (sort of like Pokemon, FB hunter edition). Exclusive Hammer and Mace squads will rarely get a kill quickly, though will also rarely take damage. A spear squad can be great or keep poking the enemy in all the wrong places - it's kind of a gamble with those guys. Put them all together, though, and you've got a very effective killing force.