[airair]

I'm hoping this will help me understand Hinge Action/Motion (sorry, as I'm still working on my terminology).

If two players wind up at impact separation with the clubhead, face and shaft in the exact same alignments all at the same speed and hitting the ball in the same spot on the face with every other alignment matching with the only difference being that one player arrived there after a Horizontal Hinge action and other player arrived there after a Vertical Hinge Action.

Which shot has better compression and why?

I think they would be the same.

I have nothing to offer as an answer, but I can join in by asking if compression and ballflight are related? The horizontal hinge action gives longer and lower shots with more roll than the vertical hinge action does, but that doesn't necessary mean that the compression is different? I don't know. But the force applied (if that is the same as compression?) - will behave differently and give different ballflights.
Testing, testing.