What is Better: Chaos set, or Black Kat Set?

Title says it all.
What do you think is better?
Personally, i have neither Black Kat helm, nor Cloak, so I cant really judge
-Witelite

the Black Kat set is better if you can get CTR elsewhere (or are using weapons you don't charge too much).
Otherwise stick with chaos.

What Flowchart said. If you have another source of CTR and/or don't use charges much, Black Kat set puts Chaos in the dirt. Not only does Black Kat have less negative resistances as Chaos, but Black Kat also gives double Freeze max resistance, meaning only +1 Freeze res is needed to resist Wisps and you can already negate Minor Freeze (such as Shiv in Lockdown). Additionally, Black Kat set makes weapons do like 8% more damage than Chaos does, and being an MSI set, Black Kat has significant advantages defensively (you'd be surprised how big effective that MSI actually is).
Which is better? Black Kat set, there's literally no competition (imo). Which would I use more? Chaos, because I don't have access to heavy CTR reductions outside of my trinkets. Currently, I just run BKC+Chaos because I like the MSI from BKC to offset my Torto shields and since I've recently gotten into the habit of using CTR/ASI trinkets instead of health trinkets, I only need one piece of Chaos to max my CTR.

Is the FULL BK set worth it?
The Cowl is definitely an item I need to get, but the Cloak? I belive it requires 6 wicked whiskers, if im not mistaken. Which means 6 margrel fights, which in turn means 6 books need to be found just to make 1 cloak. (correct me if Im wrong)
I personally always run full chaos, as its the only 5* armor I have. When I first got it, I used 2 5* wetstone pendants because I sucked at dodging. Now, that Im better (relatively) I use a Penta heart pendant, and a gun asi trinket.

You can just go with the 3* cloak. Same damage/movement bonuses and since you're already going glass cannon anyway, the lack of defense/health isn't too much of a problem.

You can also join another person.
Everyone in the party receives a Whisker when the fight is completed, while you have to be the summoner to get the Cowl.
(Also, the Cloak is 3*. The name of the item you're talking about is the Black Kat Raiment.)

Ahh, thanks for the correction
currently, I have the 3* black kat hood, and it does its job, but im afraid of getting the 3* cloak, but I suppose if I want to go glass cannon, I might as well go all the way...
#YOLO, am I right?

This is covered in the Glass Cannon section of my armor guide. Black Kat beats Chaos in the long term, by letting you max out all of your offensive abilities on all weapons (including MSI+4).

I'd say to just use your imagination on the tool tips here.
Black Kat has:
Better Damage
Freeze Resist
Movement Speed Increase
Chaos Set has:
Not as much but still amazing damage boost
Tons of charge time reduction
So which set is better? That really depends on what level your fighting, and what weapons your bringing, and what unique variants you can attain. Assuming you can get no UVs, chaos is typically better except on ice levels or whenever you don't want to charge or.. whatever, you get it. Assuming you can get any UV setup your heart desires, black kat is always better.

For the sake of argument, if you do not use UVs or trinkets, Black Kat is better when using:
- Warmaster Rocket Hammer
- Gran Faust
- Blaster lines
- Pulsar lines
- Alchemer line if you don't need the charges (Alchemers make great support guns as well as status spreaders, they don't need to be a main damage dealer, so not charging is valid here)
- Nitronome depending on how comfortable you are with bombing
- Dark Retribution depending on how comfortable you are with bombing
- Dark Briar Barrage depending on how comfortable you are with bombing
- Acheron if you don't need the charges
- Dread Venom Striker
- Winmillion
- Wild Hunting Blade (?)
- Barbarous Thorn Blade if you don't use the charge often
- Flourish lines if you don't use the charge often
- Antigua lines
- Catalyzer lines (they're fast enough already- the addition of CTR from Chaos is very noticeable but not to a great extent when you're actually using them in the field unless it's like your only weapon or something)
- Overcharged Mixmaster if you don't use the charge often
- Fang of Vog
Chaos is better for everything else.
Am I missing anything? Any weapons that are more or less debatable to fit into one of these two categories?
Well, to start, remember the defense types - Chaos resists Elemental, but Black Kat resists Shadow.
Ignoring that, looking at the wiki stats, I would use Chaos.