AH64guy pretty much nailed it.
I will add that most cheaper companies use larger ports because most cheaper users shoot ammo that is not loaded very hot.
I'll also add that after playing with mid length, intermediate, rifle and carbine gas systems, carbine, H, H2, H3 and 9MM buffers, it takes a really picky shooter to tell the worst from the best by recoil impulse when running hot ammo.
My Larue mid length is the only gun I have that runs better with an H2 buffer. Even my Colt carbine gassed guns run H buffers and eject to 4:00 with all but the hottest ammo and then they dump it at 3:00
Shoot more worry less.
