The main advantages of a dead-blow over a standard rubber mallet are the reduction of recoil and increase in striking control. The dead-blow excels in loosening stuck or stubborn parts, and also comes in handy when a breaker bar cannot provide enough leverage to turn a fastener by itself.
Stanley’s 21oz Compo-Cast is my dead-blow of choice, and my fondness for it was recently renewed. I was attempting to loosen two bicycle pedals the other day, and not even a 15″ breaker bar was up to the task. After twnety minutes of frustration, out came the dead-blow. Half a dozen strong non-marring taps later, the bolts were loosened and the pedals were free.
Sure, other striking tools would have sufficed, but the dead-blow was the easiest and most comfortable choice for this task.
I had purchased the 21oz Compo-Cast from Amazon a few months ago, but now find that MSC offers a better price. I had chosen the mid-size 21oz version because it is suitable for most light to medium duty tasks.