PMK is not as good with continuous agitation, I agree.
PMK keeps longer as a stock solution. I have had it keep seven years with no reduction in activity. Some speculate it will keep much longer than this. Pyrocat-HD has a relatively short life (about six months, perhaps twelve) once mixed. This is not an awful life compared to many stock solutions but it is not as impressive as PMK.
I like both developers. I tend to use PMK far more because the longevity is important to me (I tend to develop batches of film many months apart). I do find that PMK negatives are often much easier to print on VC paper than negatives developed with traditional developers, so in my experience, PMK certainly is compatible with variable contrast papers.