I'd speculate that the stiffness and mass/weight of diaphragm material affects the high speed performance.
I can't speak to high speed results, but I'll say that the black rubber pump diaphragms make for a noticeably easier cranking saw or trimmer, etc.
I'll toss those black plastic diaphragms out of a brand new carb, IF I have the rubber one to replace it.
Just gotta make sure the operator never runs ethanol in the unit. The ethanol causes the flaps to pucker or wrinkle and there goes the sealing and easy starts!
This leaves you at the mercy of how sticky and viscous your fuel mix is, in order to get a sealing effect then.
Thus you get all of that extra rope yanking, with the choke on, in order to get the diaphragm wet and holding a seal, when doing a cold start.
Wish I could find (and afford) to squirrel a few away for all my various OPE items.