Keith, the plunger ones are more progressive, as they lift they open the side holes, whereas the ball type blow through more directly once the ball lifts. IMHO its worth checking the blow off pressure and also being sure the PRV thread is a good fit and not loose in the cases as that can result in zero pressure to the crank. The ball type are more prone to leakage as very limited seating area if not properly seated
Several A10's here had pressure issues and I fitted a oil pressure gauge to see what was happening after a rebuild on two of mine. I run a Les Williams Triumph type and is was exceeding 80psi on start up and at idle hot. With washers added we have it operating between 60-70 PSI hot. The engine does run a timing conversion so doesn't have the pressure loss of a timing bush. I'm not far from having my stock motor running and expect the pressures to be far lower, but we've still set the blow off lower than it was as supplied.