The sword is one handed and a lot faster/harder hitting than the spear. I would consider it a must for kurasks and turoth tasks. I personally use a defender for kurasks but they do hit pretty hard on me (def 83). However, I'd rather get the task done quicker and spend a little more on food.... personal preference. Likewise you can choose whether to fight multicombat in the Sllayer Smoke dungeon with a combat familiar, or one on one in the slayer cave using a bunyip (if you do this use the teleport from the smoke dungeon, saves a lot of running...)