For pvp it's simple in that the more damage types, the more armor you can have.
example, 150 dmg, 3 damage types. well 3x45= 135, so 150-135 = 15 dmg after armor
example, 150 dmg, 1 damage type, well 1x45 = 45, so 150-45 = 105 dmg after armor.
so for pvp, if someone has no armor, maybe more dmg types would be better, if they do have armor then 1-2 dmg types max prob..
I am ok with this as long as it is more expensive to make this ammo. because for example if mob is resis to idk elec, then if you could craft a 10% pen 90% elec ammo, then you can skill very well on the mob. and normally this wouldnt be ok with me, but if it is more difficult/more expensive than normal ammo, then why not?