More than one word version:
Toss up between LC200N and K390.
I like LC for how fast it sharpens, how it holds an edge better than a lot of regular stainless steels, and obviously because its rust proof. I used my Siren a bunch yesterday and didn't notice any dulling at all.
K390 because of its silly combination of edge holding and ease of sharpening. Most steels feel like give and take. Sacrifice some corrosion resistance for toughness. Sacrifice some toughness for edge holding, etc. K390 has impressed me not only because it has truly exceptional edge holding, but its very easy to sharpen despite that. Seems plenty tough for a utility EDC and corrosion resistance is higher than 1095/O1/51200. Like SE H1 it almost feels like a cheat code. It seems to excel basically everywhere with no real draw backs.
I put a nice low grit edge on my K390 Police a week ago and haven't even thought about touching it up. It keeps slicing and slicing without slowing down at all.
The fact that I could easily get it shaving sharp off a 300 grit diamond stone with a light stropping is cool enough, but that a week later it still cleanly shaves despite going out of my way to cut anything I can with it......this steel is impressive!
I would really like to see Spyderco use this steel in a small fixed blade. Assuming its tough enough for a small camp fixie, which I believe it is, I can see it killing my love of A2. Better corrosion resistance and edge holding while still easy to sharpen.
Current carry rotation:
Pacific Salt 2 LC200N | Manix XL M4 DLC | Manix C95 foliage green | Aqua Salt