ZDP189 is a good steel for edge keeping and long term uses in a lot of EDC tasks. It can pit and have some corrosion problems if used a lot on acidic fruits and veges or flesh so cleaning it off and making sure its properly dried is a good idea. I usually treat mine like a good carbon blade just to insure they remain good looking. SG2 is my favorite steel for the added corrosion resistance it has over ZDP. Otherwise both are on par with each other I think.
I would say these two are the premo steels available today for long term cutting performances in many mediums that would torture most anything else. The friction forged D2 is supposed to be up there but so far I have not had opportunity to use any.
I quit working on the Delica and Endura 4 models for anything but low rider clip additions. The scales are quite difficult to replace since they are made in such a way that the steel liners are nested up inside them. I don't have the machining ability to do that. The ones I did work on I completely rebuilt and those were quite nightmarish also since the barrel construction is also quite unique for the sizing of the barrels. No drill bit available drills the exact size hole you need for those, not that I've found anyway, and believe me I've tried. I can get close but its either over sized too much or just under and so since the just under is the closest to the right size I end up having to ream the tar out of titanium to make each one fit and to be honest it gets old. I finally decided it was too much effort and gave it up. I'll stick with ones that are a little more precise than these end up being. I also quit working on Natives and a few others. I will work on most Spydercos but some with the nested liners can be very tricky. A few BenchMades like the Griptilians which have nested liners also are ones I don't work on anymore except for clips.
Thanks for asking though.
STR