Quote Originally Posted by Photo Engineer View Post

I was comparing two developers with very similar structures under identical conditions in my thinking. Phenidone and Dimezone-S are basically cyclic hydrazine derivatives. In alkali, the Phenidone ring opens and becomes inactive much more rapidly than Dimezone-S and the activity is somewhat lower. For this reason, Kodak used Dimezone-S in the PR-10 pods due to the high alkali content and the need for quick development.

So, for a quick OTOMH answer, those are two to compare, and if you do, (and which I have done), the Dimezone-S comes out ahead.

Yes Phenidone does hydrolyse and G.I.P.Levenson and L.F.A.Mason state that because of this Kodak & Ilford used Dimezone & Phenidone -Z which is why both Kodak & similar Ilford developers using them have a good shelf life.