I used PMK for over 7 years before I tried Pyrocat HD. The color of the stain is one variable (PMK is a decidedly green to yellow tint and Pyrocat HD is more of a brown stain) I believe that PMK may be more grainy than Pyrocat HD for smaller formats. Some may take issue with that last statement but it is my opinion. Both are sharp developers. The stain in PMK is a general overall stain that for some processes may be hard to print thru and that was one of the considerations Sandy King worked on when he was working on the formulations of Pyrocat HD. The stain seems to be contained in the image and d min seems to be clear. The last thing is PMK seems more likely to exhaust in a continual agitation situation (like a jobo). Pyrocat HD is good with continual agitation. For my applications (graded and VC paper) I choose Pyrocat HD. Good Luck on which ever you choose.