The sledgehammer is a break cue? Do they make jump cues? I have a friend that has a jump cue shaft that has (I'm pretty sure) a phenolic ferrule/ tip all in one piece. Is this what you're talking about, it's one piece (ferrule/ tip)?
The sledgehammer is a good break cue, and definitely makes jumping much easier for a person who can't figure out how to jump a ball with a normal cue. I personally like jumping with my shooting cue, because that is how I learned to jump. On extremely hard jumps I'll pool out my Mace jump cue, but it still has a normal tip/ferrule. When I jump with a Sledgehammer, I actually jump it too far and usually off the table, because I put too much force on it. Very little stroke is required for the sledgehammer. As far as breaking goes, it does break the balls very good, and you only have to hit them with a good medium speed. I'd recommend one. Everyone I know that has one really likes it. Ralf Souquet and Shannon Daulton both use one, and they are two of the tops in the world.