Both are great. K390 is going to be tougher, with a less corrosion resistance. They'll hold their edge about the same amount of time, but K390 maybe a bit longer. I think K390 is a bit easier to sharpen, as Skidoosh mentioned, but I also never had trouble sharpening ZDP on the sharpmaker; just takes a bit more time.
The ZDP-189 is not laminated on the Endura 4, but I never had any trouble with patina on ZDP.
Honestly, if you like the color of one over the other, I'd use that as the tie-breaker. Both are excellent.
Lost to the Ages: C90GRE Stretch 1 ZDP-189 British Racing Green | C28GRE2 Dragonfly 2 ZDP-189 British Racing Green
C12BK2W Matriarch 2 VG-10 Emerson Open | C81G2 Para Military 2 S30V
Currently Rotating: C81GPRGR2 Para Military 2 K390 Ranger Green | C223GPRGR Para 3 K390 Ranger Green
C90FPIV2 Stretch 2 Straight Spine, VG-10 Rit Dye'd Dark Apple Green | C223GP Para 3 S30V Green Canvas Micarta
C41BORE5 Native 5 Lightweight REX 45 Burnt Orange | C223BORE Para 3 Lightweight REX 45 Burnt Orange
C101GY2 Manix 2 Lightweight Maxamet Gray | C28GFG Dragonfly VG-10 Foliage Green
MT27 Mule Team 27 Micro-Melt PD#1 Ranger Green | C36GPGR Military 204p Dark Green