Sorry I'm arriving in this thread late, but I will take up the shield and Nunchucks to defend the Arquitens.
First off, I've got nothing against the nebulon - it's a fine ship. The Arquitens' primary advantage OVER the Nebulon is in it's side arc's strength. While the Nebulon has a great front arc, it's narrow and dodged MUCH too easily. The neb often finds itself with only a side arc shot on an enemy, and if it's obstructed at all, then no shot at long range whatsoever.
I usually prefer the Light Cruiser over the Command Cruiser. Cheaper = more ships in a build.
The Arquitens is much much better for this reason. It's more reliable. The Side arc is moderately strong and has a wide arc. And since people will often try to get up close to you, the black die at close range honestly tends to become helpful, at least for me, because I typically DON'T navigate, I typically CF, and having a red and 2 black from my FRONT, in addition to 3 or 4 red from my side, is amazing for such a cheap ship. I actually don't like Slaved Turrets on them very much, because of that exact reason. I fly lots of them in a conga line and people will often try to "Cap the T", and cut me off, the black die is great for punching through a ship that's already been softened up by long range volleys. I generally prefer TRC or Enhanced Armament, depending on my commander. (Vader gets enhanced armament, Tagge gets TRC)
The movement isn't great, I'll admit, but their side arcs COUNTER the weakness of poor movement. The Arquitens movement is designed for them to do a circular strafe - trying to keep you at long range, while circling you. It takes some practice to get used to flying this way, but the Arquiten's speed and clicks accommodate this style of flying very well. I like to fly lots of them in groups, such that a ship coming in has to face 4 or 5 volleys from them. Most ships cannot survive this, at least for very long.
I hope once they are reprinted more people will have the opportunity to fly them in larger groups. They are fun, and while the risk is high, the payoff for good red dice is huge!