I think ELMAX is a
MUCH, MUCH, MUCH, MUCH better choice for a folder and I think that for general usage folding knives that it is one of the finest choices available. While some earlier ELMAX knives had some issues (much like how S30V had some chipping issues when it was brand new and makers had not gotten the HT down 100%), most ELMAX knives made today yield outstanding performance and significant toughness that most other common knife steels cannot match (there was a recent thread where a member dropped an ELMAX folder edge-down on concrete and the blade sustained almost no damage at all!!!) If someone wants a steel capable of multi-tasking and filling any and all roles it may be needed for, the great edge holding, great toughness, and great corrosion resistance of steels like ELMAX, CPM-S35VN, and CPM-154 are the finest choices around IMO.
I'm not a fan of ZDP-189 either. In fact, I like it less by the day. It doesn't have the greatest toughness, it can sometimes be brittle, it is a pain in the ass to sharpen, it is a huge pain in the ass to sharpen if you need to do something like remove a chip, it has really poor corrosion resistance that stains easily & pits quickly, and there are newer super steels with (often dramatically) better wear resistance, better toughness, and better corrosion resistance. For the Delica, I think the VG-10 steel is a much better steel overall than ZDP-189, and especially if the knife is being used in a fashion in which toughness or corrosion resistance is a desirable trait. SuperBlue is a great steel, but there is more upkeep involved with it than VG-10 because it is very reactive.
While no test is 100% conclusive, this illustrates why I do not like ZDP-189 very much. In 2006 when it first came to affordable folders, it was the shizz. But now with CPM-M4, CPM-S90V, and M390 being common, and S110V gaining popularity, I think it is harder to justify because a steel like M390 more or less improves upon ZDP-189 across the board and by a pretty pronounced margin. Also, as this test shows, ELMAX is no slouch at all when it comes to being able to hold an edge.
So in summary of my personal opinion, the increase in edge-holding of ZDP-189 is not that big of a gain over ELMAX as it may seem, and it does not justify the tradeoff of a huge loss in toughness and a huge loss in corrosion resistance, plus the greater time in upkeep involved. To me, ELMAX is a far-superior choice in steel for a folder. And while consensus on these topics rarely exist, many Knife Makers have strong likings for steels like ELMAX, CPM-S35VN, CPM-154, etc., which says something.