Back when I was new to the game, I crafted a 2* calibur as a sidearm. It's a good sidearm for beginners. I knew from day 1 that I wanted to go as a bomber, so my other weapons were Fiery Atomizer and Radiant Sun Shards. Calibur was there to hit switches and damage bosses, and for that purpose it worked fine. As a 2* weapon, it served its purpose in T2 just fine. It hit all the switches and it didn't deal the worst damage to the Roarmulus Twins.

The charge attack is great for beginners. It's easy to use, has a good feel to it, damage is alright and keeps the user safe from crowding. The brandish does all of this and better, but it's pretty boring until you upgrade it to the T3 variants.

Let's chart out damage values at D24 again. All values are versus zombies. I didn't bother calculating them this time, 'cause Lancer Knightz have me covered.

Leviathan Blade, attack: base/max
first hit: 193/271
third hit: 241/331
charge: 355/471

Cold Iron Vanquisher, attack: +3/max
first hit: 213/250
third hit: 265/307
charge: 385/440

Glacius, attack: base/max
first hit: 270/390
third hit: 356/489
charge: 547/725
explosion: 166/230

The damage difference is pretty immense, as you can tell. Brandish has, in a nutshell, the damage of a max damage Levi at no bonus. Of course, that's due to the specialised damage being better against zombies. Let's convert this to hits and combos. Zombies, in case you've forgotten, have 1100 HP at D24.

Leviathan Blade
base combo damage: 2 x 193 + 241 = 627. 2 combos to kill a zombie.
max combo damage: 2 x 271 + 331 = 873. 1 combo and 1 hit to kill a zombie.
base charge damage: 3 x 355 = 1065. 1 charge and 1 hit to kill a zombie.
max charge damage: 3 x 471 = 1413. 1 charge to kill a zombie.

Cold Iron Vanquisher
base combo damage: 2 x 213 + 265 = 691. 1 combo and 2 hits to kill a zombie.
max combo damage: 2 x 265 + 307 = 837. 1 combo and 1 hit to kill a zombie.
base charge damage: 3 x 355 = 1155. 1 charge to kill a zombie.
max charge damage: 3 x 440 = 1320. 1 charge to kill a zombie.

As you can see, while a maxed Levi is marginally better than a maxed CIV against zombies, it doesn't meaningfully surpass a no-bonus CIV. You still have to initiate two combos to kill a zombie, and either one will kill them in three hits from a charge.

Glacius
base combo damage: 2 x 270 + 356 = 930. 1 combo and 1 hit to kill a zombie.
max combo damage: 2 x 356 + 489 = 1102. 1 combo to kill a zombie.
base charge damage: 547 + 5 x 166 = 1377. 1 charge (swipe + 4 explosions) to kill a zombie.
max charge damage: 725 + 5 x 230 = 1875. 1 charge (swipe + 2 explosions or 5 explosions) to kill a zombie.

The no-bonus Glacius isn't meaningfully stronger than the no-bonus CIV. Keep in mind that hitting a zombie with the swipe + multiple explosions is only likely with Combuster, too, so depending on which 5* Brandish you have, the CIV could kill the zombies in less time than the Brandish. However, with a Combuster, it's much easier to hit zombies with the full charge than it is with the CIV. Keep in mind that they excel in opposing situations: CIV is either at its best when you're crowded from all sides or you've got your opponent backed up against a wall/rooted to the ground, while Brandish excels in open spaces where you have every enemy gathered in on direction relative to you. Both weapons can inflict tremendous damage to a vortexed group.

Overall, I'd recommend CIV to inexperienced players using Vog or perhaps people looking for a sidearm they can take anywhere, but mostly to FSC. Combuster is the vastly better option for someone with max damage bonus (Skolver + BTS) while Glacius can work for either. If you've got a Voltedge, you probably know a lot more about swords than I care to.

Because I love charts so much, let's have a look at performance vs Kats and Howlitzers (733 health):
Leviathan Blade
base combo damage: 2 x 193 + 241 = 627. 1 combo 1 hit.
max combo damage: 2 x 271 + 331 = 873. 1 combo.
base charge damage: 3 x 355 = 1065. 1 charge.
max charge damage: 3 x 471 = 1413. 1 charge (2 hits).

Cold Iron Vanquisher
base combo damage: 2 x 213 + 265 = 691. 1 combo 1 hit.
max combo damage: 2 x 265 + 307 = 837. 1 combo.
base charge damage: 3 x 355 = 1155. 1 charge.
max charge damage: 3 x 440 = 1320. 1 charge (2 hits).

The difference between Levi and CIV turns out to be entirely cosmetic in this setting. However, CIV would reach 1 combo by just equipping a BTS or only one piece of Skolver. That wouldn't work for Levi.

Glacius
base combo damage: 2 x 270 + 356 = 930. 1 combo.
max combo damage: 2 x 356 + 489 = 1102. 1 combo.
base charge damage: 547 + 5 x 166 = 1377. 1 charge (swipe + 2 explosions or 5 explosions).
max charge damage: 725 + 5 x 230 = 1875. 1 charge (swipe + 1 explosion or 4 explosions).

As you can see, damage bonus doesn't make a very big difference for Brandish when you're solo. It's simply stacking on even more overkill. This holds great value in parties, of course.

Valiance in five words:
The most boring weapon imaginable.