I think that Chaos is currently the strongest armor type.

Why Cobalt is bad

Cobalt fails because of how it can't handle single target foes very well, with the exception of jelly cubes, which is but one enemy limited to piercing damage. If I want to wall the Roarmulus twins, my damage is going down the drain because the Roarmulus twins isn't piercing damage based, they're two mobs with one health bar that takes forever to reduce. The same goes for tortodrones and every other large mob.

Cobalt is also especially prone to bullet hell- you have to get in to use your weapon, and you cannot tank at all while charging. While doable, this still introduces extra strain on the player. Why bother using Cobalt when you can just change to Chaos?

Why Skolver is bad

A lot of people are quick to point out that Skolver has higher damage on swords. But I like to point out that the game doesn't care how high your damage per second is, it cares how high your damage per second per charge is. No matter how good a swordy I am, I'll always have to have greater risk when using a normal attack than I would from further with multiple brandish charges.

Further, the majority of strategies I've seen used to defeat the harder content in Spiral Knights revolve around charges, because most of the harder enemies punish you for using sword attacks. They do this by dealing area damage from up close, dropping poisonous splotches, surrounding themselves with fire balls, and using bullet hell against you. All of these scenarios make it very likely that you'll take damage using a sword against whatever you're fighting.

Why Chaos is good

Chaos has CTR which is mostly used at a distance as well as high single target damage, also at a distance. This combination is typically what you should be charging for. (That pun.)

The alchemers deal heavy statuses that allow you to clump together and stall mobs for lengths of time as well as snipe them with charges. If I'm using acheron or combuster, I have to walk up to a turret to hit it with a normal attack. If I'm using nova driver charge, I can deal very similar damage from quite far off with a well aimed charge attack.

The same goes for pulsars. If I fire from a distance, I deal area damage at a distance, safely. If I knock them into a corner or immobilize them, I have fairly high single target damage as well. A full party of people using this tactic works particularly well with itself. However I do not gain anything from Skolver or Cobalt; only Chaos.

Blitz needle offers high damage of all kinds from a distance. It immobilizes the user, which is a huge drawback and makes it really not all that amazing, except for against slow, frozen, or shielded mobs. When that happens, you're golden. It also helps out when you know what you're doing better than you have any right to. I can kill 3 slags in one charge after freezing them in place correctly. It has more significance, but I'll get to that later.

Brandish, Suda and Nitronome have more crowd control, and offer such great safety that I feel they are certainly worth mentioning. Having more than 2 charges per minute that deals lots of area damage gives them huge utility that they otherwise lack almost completely without Chaos-- especially for Suda/Nitro. You can almost just forgo all notion of being the most invincible awesome thing and charge indefinitely to win.

The biggest counter to Chaos are also defeated best by them. Status attacks and traps can be dealt with easily by charging from a distance, while trojans and other large shielded mobs are notably defeated by quick autogun charges. Most healing mobs rely on a mender of some sort, which can also be shut down using a charged handgun.. those with respawning healers can be dealt with using charged autoguns, to fully maximize damage taken.