If you have guns then yeah, Kat makes obvious sense. But I see people using it with striker + all swords despite this wasting the medium damage bonus, and thus only adding as much damage as a snarbo set would. I don't play a lot of LD, but humor me here:

https://zeddidragon.github.io/sk-stats/?right=c3RyIGthdCtzaDMrc3Q2K3BvMy...

In this comparison, both players have one max and two high UVs per piece. Going for 3 maxes doesn't change anything at least regarding status immunity.

Anyhow, the Snarbolax setup has moderate immunity to freeze and poison, as well as minor immunity to stun and shock this way, or any other two statuses of your choice. On the other hand, the BK setup only has minor immunity to freeze and stun and... that's the best you can get. You can overturn two weaknesses with your remaining UVs, or just go for defense, but the Snarbo set has a "high" normal defense UV built into it basically, compared to BK, so there's that.

In the context of using only swords, as a striker, these deal the same damage. So, is the BK's movement speed really worth giving up the moderate freeze, moderate poison, minor poison, and minor shock immunities for? As well as the high bonus to normal defense Snarbo has in comparison, and its absence of other status weaknesses?

Maybe BK is better with defense UVs. With a max and high shadow you can now survive three light swings from acheron, or with two max shadows and a max normal you can survive two light swings then a heavy (with a comical 2hp to spare: chances are you really just die), or a charge swipe and a whole two napalm hits (with 31hp). But all of this is assuming have two penta heart pendants and are only getting hit by max damage Acheron. Admittedly a max damage BTB/FF's basic swing does almost the same amount of damage though, so you can interchange those. Strangely Gran Faust has the same damage as well.

Even looking at damage instead though, snarbo can take three light swings from an Acheron with just one max normal UV due to the extra normal it just has built in. Unless you're worried about heavy swings, that's pretty much the same defense. Being able to walk through this or that haze bomb strikes me as a less niece concern.

A better link with defenses on the BK: https://zeddidragon.github.io/sk-stats/?left=c3RyIHNucitmcjMrc2g2K3N0NiB...

I should also add that sklover with just one max pierce UV will survive two FF swipes plus an archeon/GF backswing, same as the triple max BK set. Assuming you get hit by a FF at least twice and that all the incoming shadow attacks are 50% normal damage, Sklover with a single max is just better defensively, and only misses out on the moderate resistances snarbo has. The only remaining reason to use BK as a striker is gun damage and MSI. Phantomos against the max shadow BK does like a half of what it would if used back on the sklover.