Gather Around, commanders! I have updated tactical information about this sucker.
Firstly, according to rumors, the Ta'unar will be having a points hike when the new Imp. Armor comes out...And I agree with it 100% after my last battle with it.
I faced an Imp-guard player using the 3-baneblade formation, along with a 4th (stormblade in his HQ slot). All I had on my side for Superheavies was my Supremacy Armor.
In a 4000 point game, the supremacy armor killed a spectacular sum of units. It was equipped with Fusion Eradicators and the Heavy Rail Cannon Array.
Firstly, everyone's complaints about the heavy rail cannon array are unfounded. Out of several battles with it, I only missed once because... i was shooting it at something NOT a superheavy (I shot at a dreadnaught). Remember that your maximum scatter is 8 inches, and most superheavies are bigger than that number. If you miss, the dice gods really hate you, or you are being a cheeky ork and shooting it at odd targets... not that I wouldn't...but still.
The mass induced targetting does horrible things to baneblades...or titans for that matter.. or anything superheavy. you have a 1/3 chance of the Destroyer! result, and that result is what erased the Shadowsword from the table, and the fusion eradicators? out of ten shots I hit five times, but penetrated all five times, three of them were 5's and 6's. ONE fusion eradicator destroyed the Stormblade ALONE
Now, this is not to say the Supremacy armor isn't invincible. It took two rounds of shooting with more lascannons then was reasonable, but it did finally die. The amount of time and effort that went into killing it resulted in the destruction of the other super heavy tanks shortly after simply due to the Riptides and Ghostkeels he had to ignore to kill the Supremacy Armor. What did this tell me?
Firstly, the Supremacy armor is NOT a defensive weapon system with this loadout. You need to move close to get your eradicators in range, and the rail cannon is a *BAD WORD DELETED* beast. The mortars ARE effective even without ignores cover (I have killed plenty with them).
If you are looking to be defensive, you can always swap out the arms for the tri-axis and take the driver, however, depending on your enemy, the missiles WILL be a better bet, especially against swarm armies like orks and bugs. (Trust me, the Nexus is GREAT against orks and bugs. Blind screws them over in ways you cannot imagine.) Consider the Nexus to be our Vulcan Mega-Bolter. It's a swarm killer that has the advantage of being really good against normal vehicles. If you are worried about gargantuan creatures, take the tri-axis, if you are worried about knight titans, take the eradicators.
The munitions driver IS good against elite armies like termies, necrons and marines. Especially armies with the big 'decurion' formations that are all but unkillable without the D. With a massive 7 inch blast D, you can surgically remove them from the table while still having something for super-heavy units.
Comparing this to the Stormsurge is a far more complex game then I thought. The Stormsurge is effectively gun. it's nothing BUT gun. It's a giant gun with more guns attached to more gun. Did I mention gun?
Unlike the Ta'unar, there is only really one effective choice when it comes to weapons, the Driver is far superior to the Blaster. Yeah you can get the D and more shots out of it, but the range is pathetic and nothing should -ever- get that close. If you want the D, you have the missiles for it and those should be more than enough to remove any unwanted target from the board (just be sure to have the marker lights to back it up, you will need them.) You CAN take 3, but at that point you are looking at investing a huge amount of points (and money!) into a unit that WILL NOT MOVE and is a HUGE target. Don't fool yourselves, you will be spending the game defending them, NOT taking the fight to the enemy.
Between the two, I would take the Supremacy armor, simply due to durability and flexibility.