A Super Star Destroyer or a Borg Cube?
Okay, well, I wanted to match the SSD up against something, but I couldn't think of anything that wasn't insanely more powerful than the SSD, or much much weaker, so I thought a Borg Cube would be a good match up.
There's the Super-class Star Destroyer. For refference, the tower at the rear of the ship is supposed to be the same size as that of a standard Imperial-class Star Destroyer, I believe a SSD is 11 times larger than a standard Imperial SD, and comes to a whopping size of (I believe) just under 13 kilometers. (12.8, I think)
It has 250 turbo laser batteries, 250 heavy turbo laser batteries, 250 concussion missle tubes, 250 ion cannons, 40 tractor beams, and is decked out in a titanium reinforced Alusteel hull. It also had 12 squadrons of TIE-fighters, four of each (TIE-fighters, TIE-interceptors, TIE-bombers).
Onboard, it also had a full Stormtrooper corps of 38,000 troops, 25 AT-ATs, 50 AT-STs, various ground vehicles, and three pre-frabricated garrisons, ready to land on planet.
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Now, onto the Borg Cube.
This mammoth is said to be several kilometers both long and wide, and its crew is said to contain "thousands of Borg." Other than that, not a lot of specs are avalible on the Borg cube, other than the fact that it's really, really huge, about one fourth the size of Earth, has a LOT of guns, can "adapt" to weaponsfire and missles just as the Borg themselves can, and is really, really huge.
Anyway, this would be a really close battle, and I'm still not quiet sure. The SSD I feel would have an advantage in the beginning, but if they didn't destroy it fast enough, the Borg cube would adapt to their turbolasers, and then their heavy turbolasers, and even their Ion cannons. I suppose the wings of TIEs could help out, also, as they fire shots at different frequencies, and the Empire could send over Stormtrooper boarding parties, but they'd eventually adapt to that, as well...
I suppose it just depends on how fast the SSD responds, but if this is, say, the Executor with Admiral Piett, or even Darth Vader on board, I'd have to say the SSD would win.