Having only done and fielded one, I'm partial to the shadowsword. The volcano cannon is just nasty and good for dealing with knights and any heavy tanks plus you have all the heavy bolted and lascannon shots. Not to mention it just looks epic.
Well.. I have a bunch of Leman Russ hulls (10), a Malcador Infernus, a Macharius Vanquisher, and a Stormblade (baneblade with a honking big plasmacannon) a bit of artillery, and a boatload of infantry. In short.. a bunch of stuff.
It's not so much about what my army needs (what army really needs a second baneblade hull? ) but more about me trying to make up my mind as to how to build it. They all look cool, they fill a role, etc. So I keep bouncing back and forth between options.
Str D is lacking in my army, but so is high RoF ap3. The hellhammer(?) has a beast of a gun with ignores cover, the baneblade itself looks very flexible in its target selection, etc.
So I'm mainly just curious what it is that people enjoy about their superheavies (before they blow up)
I ended up going with "most of them, most of the time"
The hull is currently built so that I can switch around between the non-turreted versions. I just need to get some stronger magnets to hold the guns to the mounts, so that the longer barrels don't droop down.