Swords

Fallout Plays put together a terrific in-depth analysis of everything Swords. If you know of any other content, please let me know!

Sword Frames

Lightweight: Usable only by Hunters. There are two of these swords.
Adaptive: Usable by all classes. While Warlocks do not have a specific type dedicate to them, they do have unique access to the Infinite Guard perk.
Aggressive: Usable only by Titans. There are two of these as well.

Charge Rate: How fast your Sword Energy replenishes, which is what gates your ability to block and perform heavy attacks. Swordmaster’s Guard is the only Guard that increases Charge Rate which (for Falling Guillotine at least) means you can use your Heavy Attack ~0.5s more often.
Guard Endurance: How fast your Sword Energy depletes while in the guard animation.
Guard Efficiency: How fast your Sword Energy depletes while getting shot.
Guard Resistance: How much damage your Guardian takes while… guarding.

They deplete your Sword Energy!
When your Sword Energy is full: Uses 4 ammo, does maximum damage.
When your Sword Energy is not full: Uses 1 ammo, does significantly less damage. The learning here is that you probably never want to be spamming Heavy attacks!

Lightweight and Adaptive frames must use a Heavy attack to kill a roaming super. Aggressive frames can use a Light attack.
You’re probably going to want to focus on Guard Efficiency and Guard Resistance.

En Garde: In PvP, a light attack can already kill a guardian. No need for it in PvP. In PvE, the duration is 1.5s. There are better options.
Assassin's Blade: 15% extra damage + faster sprinting for 5s. In PvP, damage doesn’t matter. Movement speed is fun.
Shattering Blade: +25% extra heavy attack damage when depleting ammo. Pass.
Surrounded: Not necessary in PvP - not only because you’re unlikely to proc it, but that a single light swing already kills full health guardians. In PvE, solid! +25% base, +35% with Surrounded Spec!
Whirlwind Blade: Premier damage-dealing perk! Stacks to five, once per light swing. +6% per stack to 30% (x5) with a 3.5s duration. Each hit extends the duration.

Energy Transfer: Straightforward, works great, nice to have but “eh”.
Counterattack: You have to take damage right when you activate guard.
Flash Counter: Debuffs the enemy that attacks you. They take 20% more damage from all incoming damage! This is the counter to ground-pounder bosses. This only drops on the Honor’s Edge sword.

Tireless Blade: Only gives you 1 ammo back after multiple heavy attacks. Pass.
Relentless Strikes: Gives you back sword ammo on repeated hits. Seems like it’s bugged currently and giving you more ammo back than it should. Pairs great with Whirlwind Blade.