The higher rpm PDP hybrid does have a different crankshaft, so perhaps the regular PDP .61 is better as a lugger and the PDP hybrid is better for go-fast piped applications.
I have a couple HB .61s which are said to be basically a West German version of a K&B .61. Neither of mine are PDP though. One is gonna be used in my Mig-27 Foam target drone plane. Easy starter and good runner albeit the muffler is pretty "barky". I wonder if the K&B variants use a different muffler?