Introduced in The New Jedi Order are a unique class of ship called the Bothan Assault Cruiser. I'd like to take a look at these ships and determine just how much information we can about them.

"The Bothan Assault Cruiser was one of the latest additions to the New Republic fleet. While slightly smaller than a Victory-class Star Destroyer, and possessed of leaner and less angular lines, the Ralroost boasted 20 percent more firepower than a Vic and almost half again as much in terms of shielding and armor. The ship had been designed to take a pounding and still hammer an enemy." (DT/O, 59)

"The fighter hangars were amidships and had launch apertures that would let the fighters head up or down, as needed, to get into battle. The dual launch paths also meant recovering fighters after a battle was much faster ... " (DT/O, 59-60)

"Ralroost shuddered to a hit ... a Bothan Assault Cruiser was so named because it concentrated most of its power on attack, not to shields or defense." (DW, 387HC)

"Distant rumbles echoed through the room as Ralroost's inadequate shielding absorbed hits." (DW, 400HC)

The original source of the Bothan Assault Cruisers, Stackpole's Dark Tide duology, clearly states that they are superior to a Victory-class Star Destroyer, whose role they seem intended to take over. Their firepower is significantly greater, as is their protection - 150% shielding and armor of a standard Vic. While I have great respect for Walter Jon Williams as a writer, his technical knowledge of the Star Wars galaxy has been shown to be minimal. In fact, he himself admitted that he was given a "crash course" in Star Wars EU prior to writing Destiny's Way. His book shows clear indications of this, and it is for this reason that I choose to accept the description of Michael Stackpole, a veteran EU writer and the creator of the ship, over Mr. Williams' description of Ralroost. Given that Victory-class Star Destroyers are still in use by both Republic and Remnant forces, and presumably Hand of Thrawn forces as well, the VSD shields are clearly not completely useless, as they would have to be for a Bothan Assault Cruiser's shields to be both stronger than a VSD's and yet inadequate for defense.

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Turning now to Wizards of the Coast's reference guides:

Bothan Assault Cruiser (SoG, 90)
Length: 850m
Crew: 1,240
Passengers: 250 (crew + pilots)
Hull: 7D = 7-42
Shields: 4D+2 = 6-26
Weapons:
-20 Turbolasers (7D)
-24 Heavy Double Turbolaser Cannons (4D)
-10 Ion Cannons (4D)
-20 Proton Torpedo Launchers (9D)
-4 Tractor Beam Projectors (6D)
-4 Fighter Squadrons

Victory Star Destroyer (ISB)
Length: 900m
Crew: 4,798
Passengers: 2,040 (troops)
Hull: 4D = 4-24
Shields: 3D+1 = 4-19
Weapons:
-10 Quad Turbolaser Batteries (5D)
-40 Double Turbolaser Batteries (2D+2)
-80 Concussion Missile Tube Launchers (9D)
-10 Tractor Beam Projectors (5D)
-2 Fighter Squadrons

Victory II Star Destroyer (ISB)
Length: 900m
Crew: 5,881 + 226 gunners
Passengers: 1,600 (troops)
Hull: 4D+2 = 6-26
Shields: 3D = 3-18
Weapons:
-20 Turbolaser Batteries (7D)
-20 Double Turbolaser Cannons (5D)
-10 Ion Cannons (4D)
-10 Tractor Beam Projectors (6D)
-2 Fighter Squadrons

Since the hull code includes particle shielding, it won't be an exact comparison of shields vs. armor, but we can at least get a rough estimate of how the ships stand up to each other.
Hull: The Bothan Assault Cruiser's hull is significantly better armored than the Victory Star Destroyer. 150% may be slightly low, but it is roughly correct.
Shields: The Bothan Assault Cruiser has significantly better shielding than both the Mark I and Mark II models. Again, 150% is a relatively accurate figure.
Firepower: This is a more difficult figure to quantitatively assess, but the Bothan Assault Cruiser significantly outguns the Mark II VSD. The Mark I VSD is dangerous because of its 80 Concussion Missile Tubes, which give it the firepower to inflict heavy damage upon a capital ship, space platform, or planetary surface in a hurry. However, its energy weapons are vastly inferior to the Turbolasers and Heavy Double Turbolaser Cannons aboard the Bothan Assault Cruiser.

Side note: I've chosen to ignore the so-called "wild die" roll. Speaking of which, a ton of thanks to jSarek for providing VSD stats and helping me out with this part of the analysis.

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The Bothan Assault Cruiser was announced some time after the Remnant/Republic peace treaty. Some people considered it "either a foolish allocation of resources, hints at future Bothan aggression, or ... a gross waste of money." (DT/O, 59) Construction on the first shipment appears to have been finished shortly before the Yuuzhan Vong first invaded at Sernpidal, Helska, and Dubrillion/Destrillion.

An image of the Bothan Assault Cruiser can be found here. The launch apertures to the hangar bay aren't visible in this picture, but there are apertures dorsal and ventral allowing fighters to scramble quickly. (DT/O, 59) The bay itself is amidships, probably preventing a lucky shot gutting the entire fighter complement of a cruiser. It's also possible that the launch apertures seal when not being used.

Just aft of the fins, the outboard drive nacelles (BP, 3HC, 5HC) are visible. The structures outboard of the fins may be weapons emplacements.

Champion, the Bothan Assault Cruiser at Kalarba, was modified so its fighter bays were mounted port and starboard (BP, 3HC). It is unknown whether more than one Assault Cruiser was constructed with this modification.

Construction of these vessels likely takes place at Bothawui and the primary colony on Kothlis. It is probable that the Bothans decided they needed capital ships of their own to defend themselves in case of future problems with other Republic members, as the light capital ships and starfighters of various Bothans' private armadas were insufficient to deter the Ishori-led coalition above Bothawui. The Ishori and their allies were only held at bay by the Diamala and Mon Calamari; doubtless the Bothans were unhappy having to depend upon others, especially the Mon Cals, for their protection and began to arm themselves.