I have an Open pistol with two barrels that shoots 9 major or Super or Supercomp.
I was expecting a softer flatter feel from super/sc and, even after trying many powders, I did not get it.
Smiths have figured out the 9 major so reliability is no longer a differentiation.
If you buy once fired single head stamp 9mm brass, shoot it once in practice, pick it up and reload it for matches and leave it on the ground you'll have nice reloading experiences and good ammo at two cents a case or so. And no scrambling at matches for your super brass.
I recommend 9mm major.